LSx Harness Rework

I want to start documenting the work I'm doing on my harness publically somewhere, so please bear with me as I'm still in the process, but have a lot of work I want to put down while it is fresh in my mind.  I'm linking this page to the easy 5.3 swap, so post any thoughts or comments there.

At this point I'm going to split what I have done into 3 parts.

• ECM Relocation
• Additional, Modified, and Removed Sensors/Circuits
• Integration with 2nd Gen S Truck Electronics

A great resource for schematics, diagrams, etc is LT1Swap.com.  I'll post up some that I have made, but they won't be all inclusive.

http://www.lt1swap.com/wiringharness.htm

For factory S Truck wiring this is a decent public resource:

1983-2004 S10 Schematics

I do want to note that I'm starting with a 2003 L59 5.3 harness.  It is setup for both flex fuel and throttle by wire and I will be keeping both including the fuel composition sensor.  I may have a chance to add info on swapping those systems in or out at a later time.  Ryo (greencactus) might be able to provide more info on wiring for the cable throttle as well as building a stand alone harness.  Mine will be plug and play to the factory Blazer wiring.


Table of Contents

• Introduction
• Preparing the Harness
• Part Numbers
• ECM Relocation
  
  • Introduction
  • Injectors
  • Coils
  • Other Circuits
  • UBEC Location
  • Further Thoughts
• Additional Circuits
  
  • Introduction
  • Engine Oil Temperature
  • Transmission Oil Temperature
  • Manual Transmission
• Integration
  
  • Introduction
  • Starting
  • Gauges
  • Fuel
  • Cruise

LSx Harness Rework – Preparing the Harness

To prepare the harness for modification, I first labeled all of the connectors that weren't cut off before I got the harness.  I used large toe tags and taped a label with a picture of the connector and the pinout diagram to the tag.  On others I didn't have a label for, I hand wrote the pinout and wire colors onto the tag.  It was very helpful once I started modifying and removing circuits.  I do highly recomend labeling any wire that is removed from a connector.  Even those that are expected to be left out permanently; "just in case".


IMG_3000 by TheHarley, on Flickr


img_2931 by TheHarley, on Flickr

I then removed the wire loom, which allowed me to both trace wires back to their origin that were cut and label the cut circuits.  It also made it extremely easy to layout the wires where I wanted.  I have yet to take the harness completely apart and that has helped me keep its basic original shape while keeping everything organized and in one piece.  Others do have success completely breaking the harness down into the individual connectors and reassembling.  Choose a method that is comfortable.


img_2935 by TheHarley, on Flickr

LSx Harness Rework – Part Numbers

I dug around the internet and parts catalog to come up with the part numbers for the connectors, terminals, and any other parts I would need to make the harness complete.  Again note that these are numbers specifically for my swap.  If you’re having trouble finding a part number for a connector or the like ask and I will see what I can do to help.  Anything extra I do find I will do my best to add to a list here.  Most of the terminals and seals are the same across several connectors and gage sizes, so that helps when buying in bulk.  I don't think I ordered much more than a half dozen styles of terminals.

So far I have ordered all of my harness parts from mouser.com, but there are other sites out there.  I have been very happy with mouser.  I’m using a crimp tool similar to Delphi 12085271, but don’t know the exact part number off the top of my head.  I really like the ratchet mechanism and the extra joint helps keep the crimps straight although I think the factory has an even better tool to hit it straight on.

2003 L59 5.3 Connector and Terminal Part Numbers


Connector Part Numbers - Engine by TheHarley, on Flickr

T56 Connector and Terminal Part  Numbers


Connector Part Numbers - T56 by TheHarley, on Flickr

LSx Harness Rework – ECM Relocation – Introduction

From the factory the full-size trucks (4.8, 5.3, & 6.0) have the ECM coming off the engine at the front of the driver side head.  This doesn't match up with the factory S Truck position or allow the PCM to be easily placed in the cab without cutting and extending the entire harness.

To solve this issue I simply swapped the injector and coil wiring from side to side and then flipped the wire bundle for the ECM from the front to the back of the engine.  Now the mass of wires is coming off the engine at the rear of the passenger head.  This both matches the stock 4.3 layout as well as provides the opportunity to put it through the firewall for mounting under the dash or on the transmission tunnel.  I don't have a measurement, but I'd estimate 3 feet of wire now between the engine and the PCM.

Obviously just moving the connectors will have the PCM powering the wrong injectors and coils, so there are some wires that need to be moved around.  Fortunately this can all be accomplished at the PCM connectors, by simply pulling the appropriate pins and switching them around to line up with the appropriate cylinder.

LSx Harness Rework – ECM Relocation – Injectors

I started by drawing before and after diagrams of both the injectors and the coils, relating the color of the wire to the cylinder.  With that I was able to see what color belonged to which circuit and swapped them apppropriately.  For example the cylinder 1 fuel injector originally uses a black wire, but when the harness is flipped it now has a light green/black wire.  It still needs to be powered by circuit 1744 coming out of pin 36 on the PCM - C1 (Blue) connector.  So the black wire is pulled from pin 36 and replaced by the green wire from pin 4.  Notice in the pinouts below how everythings stays the same, but the color.  The circuits aren't changing, just the color of the wire the cirucit is using to reach the injector.

Fuel Injector Layout Sketch


Injectors & Layout by TheHarley, on Flickr

PCM Connector


PCM Connector by TheHarley, on Flickr

Original Connector Pinouts for Injectors


Injector Pins - Original by TheHarley, on Flickr

Modified Connector Pinouts for Injectors


Injector Pins - Modified by TheHarley, on Flickr

The fuel injectors also use two ignition circuits from the UBEC connector, C2. It probably isn't necessary, but I swapped those as well just to keep the factory circuits going where they were designed.  To do this switch pin D10 with E10 and pin C10 with E6.  They are all pink wires.  If using the 4.3 fuse block some of these circuits will move again, but that will be covered in a later post.

UBEC - C2 Connector


UBEC Connector by TheHarley, on Flickr

LSx Harness Rework – ECM Relocation – Coils

The coils are somewhat different than the injectors.  The coils, brackets, and sub harness, are the same part from side to side; the bracket isn't mirrored.  The picture below shows this.  This isn't difficult to change in the wiring as there is an in line connector at the bracket for each side.  From the factory the driver side uses solid colors and the passenger side uses the same colors with a white stripe.  So simply swap the solid color wire with the white stripe at the PCM and the ignition signals are swapped.  Again notice how nothing, but the color of the wires change.

Coil Layout Sketch


Coils by TheHarley, on Flickr

Original Connector Pinouts for Injector Coil Signals


Coil Pins - Original by TheHarley, on Flickr

Modified Connector Pinouts for Injector Coil Signals


Coil Pins - Modified by TheHarley, on Flickr

As with the injectors the power and low reference circuits are different for each side of the engine.  It probably isn't necessary, but I swapped these as well.  For the power leads I swapped pins B9 and D9 on the UBEC C2 connector.  They are both pink wires.

For the low reference I swapped the brown (Pin 60) and brown/white (Pin 61) wires on the PCM C2 connector (Green).

LSx Harness Rework – ECM Relocation – Other Sensors & Circuits

Some of the other sensors also need their circuits rerouted while doing this.  The alternator and Engine Coolant Temperature sensor are at the front of the driver head.  I cut these out before laying it out on the engine the first time because I thought I knew I had to lengthen them, but I'm now second guessing that.  I suggest not cutting them until they're laid out on the engine and, in fact, they may end up being more than long enough.

The Throttle Control (Drive by Wire), MAF, Crank Position Sensor, and Starter Signal I bundled with the injectors and coils on the passenger head.  The Throttle Control was bundled with the original inj/ign circuits here and I'm going to locate my intake and MAF on this side since the battery is relocated.  The Throttle Control will be about a foot longer than it needs to be now.  The MAF will depend on its final location.  The Crank Position Sensor and Starter Signal were originally routed from the front of the driver head down the side of the block with the A/C compressor circuits, across the front, past the compressor and back along the passenger side of the lower block.  The crank sensor is located behind the starter on the rear, lower, passenger side of the block.  I routed both instead with the passenger inj/ign, down the front of the block and back to avoid the heat of the manifold.  It actually appears to be the correct length to do this, so I doubt it will need to be modified.  If A/C is being run in the stock position I'm guessing it could be run with the Crank Sensor circuit too.

Crank Position Sensor Factory Wire Routing


Lower Passenger by TheHarley, on Flickr

Oil pressure, Cam Position Sensor, and knock sensors will all have an extra foot of wiring and can be shortened too.

The O2 Sensors, Fuel Composition Sensor, and Engine Oil Temperature Sensor I'm tying into the transmission harness to keep them away from the heat of the manifolds.

LSx Harness Rework – ECM Relocation – UBEC and Control Module Location

On the full size trucks the Underhood Battery Electrical Center (UBEC) is near to the PCM as well as most of the other control units and in line connectors (TAC module, Dash Connector, Chassis Connector, etc.).  If this route is taken those will need to be accounted for.  I'm making all those connections inside the cab and mounting all the modules and UBEC there too.  If the factory S Truck mounting location of the UBEC is desired the C2 UBEC connector and wiring will have to be rerouted through this harness, but fewer wires will have to be extended than if this swap wasn't done.

LSx Harness Rework – ECM Relocation – Further Thoughts

I was able to remove about a foot of wire from the new driver side injector and coil harness.  It is quite obvious, looking at the sketch for the injector layout, that there is extra wire when the harness is swapped around.  I've got a pile of terminals for the PCM and a crimper, so I cut it to length there and crimped on new terminals.  Overall, I'd say, I'm actually removing more wire than I'm adding, which is a huge driving force in approaching the PCM relocation this way.

Lastly, depending on the goals for the harness a similar result could be accomplished by simply flipping the injector wiring front to back on just the driver side to get the harness bundle coming off the engine at the back of the driver head.  Following the same process I did for the full swap shouldn't be complicated.

LSx Harness Rework – Integration – Introduction

The engine harness connects to three other harnesses within the vehicle, the body, the chassis, and the Underhood Battery Electrical Center (UBEC).  Depending on the model year of both the engine and the truck the integration will look slightly different.  I will try to provide thoughts and extra diagrams that don't pertain to my swap, but I will mainly focus on putting a 2003 5.3 with electric throttle into my 2000 Blazer.

The following diagrams document my current layout of these three connectors.  Lines in green are circuits I added.  Lines in orange are existing circuits I moved.  On the UBEC C2 diagram the second column in red is where the wire moved from originally on my 2003 5.3 harness.  The grayed out letters are existing and unused circuits in the 4.3 UBEC.

UBEC - C2 Connector


UBEC - C2 Pin Diagram by TheHarley, on Flickr

Body to Engine - C100


C100 Pin Diagram by TheHarley, on Flickr

C100 Relocation notes


C100 Pin Relocation by TheHarley, on Flickr

Chassis to Engine - C104


C104 Pin Diagram by TheHarley, on Flickr

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There are four systems I have found I needed to integrate the 5.3 with the S10 electrical.

• Starting
• Gauges
• Fuel
• Cruise

Some other systems that I'm not integrating, since I removed them on my truck, could include:

• EVAP
• Air Conditioning
• ABS/Traction Control
• 4 Wheel Drive

LSx Harness Rework – Integration – Starting

There is a simple way to do this, but with a newer ECM there is also the option to let the computer control starting, which adds some complication to the wiring.

Without using the computer simply ground pin F7 in the C2 UBEC connector. I moved the ground in the 5.3 harness from pin B7 to pin F7 to accomplish this since there are other circuits that use that ground pin too.  Everything else is in place to work with a manual transmission.

Original 2000 Blazer Manual Transmission Starting Schematic


Manual Transmission Starting (2000) by TheHarley, on Flickr

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With the 2003 ECM I have the ability to use the computer to control starting.  If you haven't started a newer GM vehicle it is as simple as touching the key or button to the start position and the computer controls the rest.  May not seem like a huge upgrade, but I've found it convenient to have the one touch start; I can let the computer handle it while I'm doing other things to start my drive, such as buckling in.  It is also one step away from a push button start.

From a wiring standpoint, using the factory 4.3 Fuse Block from my Blazer, wasn't the easiest task.  The wiring itself isn't hard to modify, but there were some hard decisions to be made to get it to work easily.  The problem with the Blazer Fuse Block is the starter relay signal grounds inside the fuse block along with several other circuits.  The 5.3 ECM uses the signal ground to shut down the starter once it has determined the engine is running on its own.  Unfortunately the other grounded circuits need power at times other than while the engine is cranking.  My solution was to find another relay within the fuse block I won't be using that has an isolated signal ground.

Further complicating matters for me is I have already relocated the battery to the back of the Blazer and use a second solenoid to remove power from the 10 feet of starter wire while it isn't starting.  This did help my decision in the end, but took some seriuos review of all my schematics.  One other aspect I considered was the fuse block connector the relay used.  The fuse block has several connectors each distributing circuits for certain parts of the truck - engine, chassis, body, lighting, etc.  Getting signals between the different systems can be difficult without adding connectors between, which I'm trying to avoid.  With the ECM controlling a solenoid that is part of the body harness I was limited.  This was a problem with the Backup Lamp circuit too.

UBEC Connectors


UBEC Connections by TheHarley, on Flickr

I ultimately decided to use the existing rear defogger relay.  It has an isolated signal ground and the relay output goes to the body.  Unfortunately the signal ground was part of the body too, so I had to populate an extra pin of my body to engine connector to use it, but in the long run this was negligible.  The big advantage for me is the output already has a wire run to the back of the Blazer to hook up to my additional starter solenoid.  I don't believe this circuit can handle the current needed for the factory solenoid, but it is sufficient for the solenoid I have relocated with my battery.  The rear defogger is on a 30A fuse and the starter relay uses a 40A.  I cannot suggest using this relay without taking that into account.

2003 5.3 Manual Transmission Starting Schematic in a Manual 2000 Blazer w/relocated Battery


Manual Transmission Starting by TheHarley, on Flickr

The crank signal (PPL 806) needs to be sent to the PCM, so using that circuit available in the UBEC C2 Connector (Engine) is the easy choice.  Move the Purple wire from pin F3 to F5.

The PCM needs a signal from the clutch switch to prevent a start in gear.  Since the switch is already part of the body harness just swap the purple wire from pin C3 to D9 within the UBEC C1 Connector (Body).  Wrap up the clutch signal by adding it to the C100 Body to Engine Connector.  On the body side I moved the purple wire with a white stripe from the UBEC Connector C1 (body) to C100, pin N.  On the engine side I moved the dark green wire from the UBEC Connector, C2 (Engine) to C100, pin N, again.  This will send the signal to the PCM at pin 18.

The relay signal grounds through the PCM C1 Connecter (Blue) at pin 39.  Circuit 193 originally terminates at pin B6 of the C203 Connector (I/P to Body) that is located behind the glovebox.  Move the white wire from there to the C100 Body to Engine Connector.  I used pin J.  On the engine side the yellow wire with a black strip from pin D12 in the UBEC C2 Connector (Engine) needs to move to the C100 connector at pin J.

After that the output from pin B8 in the UBEC C1 Connector (Body) needs to go to the solenoid.

LSx Harness Rework – Integration – Gauges

The factory S truck gauges actually play quite well with the 5.3 engine sensors.  The only hurdle I had is, starting in 2003, the Oil Pressure sender was changed; the signal in the 2003 harness is sent through the PCM to the Instrument Cluster over the serial data signal.  This isn't how the S10 gauges work, so I purchased an Oil Pressure sender for a 2002 5.3 using part number 19244505.  This can use the same connector as the 4.3 and 2003 5.3, but I sourced one from a 2.2 since it matches exactly with the single pin.

2002 Oil Pressure Sender



4.3 plug on the left.  2.2 on the right.



I'm actually leaving the wiring for the 2003 pressure sender in case I decide to do something different for gauges, but those circuits can be removed.  The three circuits trace back to the PCM; the Gray wire and Black wire to pin 7 and pin 63 of the C1 connector and the Tan wire with a White stripe to pin 58 of the C2 connector.

The 2002 Oil Pressure signal goes directly to the gauge through the C100 connector using pin C, so add a Tan wire with a White stripe between C100 and the pressure sender.


PCM, Data Link Connector (DLC), Engine Oil Pressure Gauge Sensor by TheHarley, on Flickr

The engine speed signal for the tachometer comes from the PCM using pin A in the C100 connector.  On the engine side grab the White wire that is originally located in pin K of the C100 connector and move it to pin A.


Power by TheHarley, on Flickr

The Vehicle Speed Signal (VSS) is the other tricky part.  The 5.3 only has one VSS signal going to the body, but the Blazer had two.  Removing the Cruise Control Module (CCM) helps out in my case because I am able to simply move the VSS signal from the CCM to feed the Instrument Cluster.  This requires moving the Dark Green wire with a White stripe from pin K of the CCM connector to pin E11 of the C203 Connector (I/P to Body) that is located behind the glovebox.  A Green wire will already be here, but it needs to be removed and replaced with the Green/White.

Back to the engine harness the Dark Green wire with a White strip that is originally located at pin D in the C100 connector needs to move to pin M.

Next the Multifunction Indicator Lamp (MIL) signal needs to be routed to the Instrument Cluster.  In the engine harness the Brown wire with a White stripe needs to be moved from pin G in the C100 connector to pin L.

The serial data signals also need to be moved to match up with the Blazer wiring.


SP201 - Serial Data by TheHarley, on Flickr

As shown in the C100 connector pin diagram, at the beginning of the section, this is straightforward.  With the engine harness C100 connector move the Yellow wire from pin M to pin H and then move the Dark Green wire from pin H to pin R.

LSx Harness Rework – Integration – Fuel

Chassis to Engine - C104


C104 Pin Diagram by TheHarley, on Flickr

The fuel pump and sender wiring may be the easiest integration between the 5.3 engine harness and the truck.  It all passes through the Chassis to Engine connector (C104) and since these are the only chassis circuits I'm keeping I downsized to the Blazer's 6 pin connector.  Both circuits already reside in the larger C152 connector.  Depending on where the PCM is mounted the wires may need to be replaced and/or extended to reach the location of the S Truck connector.  I'm revising the chassis side of the circuit as well, but don't know how it will be laid out at the moment.

What I do know is the low reference circuit using the Black wire needs to be moved from pin J of the C152 connector to pin D of the C104 connector and the Fuel Level Sensor Signal using the Purple wire moves from pin K of C152 to pin E of C104.


Fuel Gauge by TheHarley, on Flickr

The only other changes required are the signal and ground for the Fuel Pump Relay.  If it hasn't been done already move the black ground wire from pin B7 to pin F7 in the 5.3 engine harness UBEC C2 connector.  Next move the Dark Green wire with a White stripe from pin A7 to B7.


Fuel Pump Controls by TheHarley, on Flickr

Lastly I am adding the wiring to run a second fuel pump with the PCM.  Many of the Gen III/IV engines came in vehicles with either a second fuel tank or a tank with two chambers, so a second pump control is part of the software.  If I ever get to a point where I need more fuel this may provide a solution I can just plug and play.  This does require adding an additional relay to the engine harness, but 30A sealed relays are plentiful on S Trucks.

The schematic is straightforward and since the wires won't likely be in place I am just posting it for reference.  I'm using pin F of the C104 connector to pass the power feed from the relay to the pump, but will cap it off on the Chassis side for now.

LSx Harness Rework – Integration – Cruise

Cable Throttle

Using the factory Cruise Control Module with a cable driven throttle body is quite easy from my understanding.  The module needs two inputs from the PCM: a Vehicle Speed Sensor (VSS) signal and the cruise control engage signal.  VSS comes from pin 50 in the C2 connector of the PCM and the cruise engage is pin 13.  I will post up the schematics below of the factory S Truck wiring since there are several different combinations that could be used.  If these don't cover a model year let me know and I can probably dig it up and share.

2000 Blazer Cruise Control & PCM


2000 Blazer - Cruise Control Module and VCM by TheHarley, on Flickr

2003 Blazer Cruise Control Engage Signal


2003 Blazer - Clutch Pedal Position Switch, Stop Lamp Switch, PCM and Cruise Control Module by TheHarley, on Flickr

2003 Blazer Cruise Control VSS


2003 Blazer - Gauges by TheHarley, on Flickr

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Electronic Throttle

With the electronic throttle all of the CCM inputs must now go to the Throttle Actuator Control (TAC) Module, which is part of the engine harness rather than the body.  Other than the ignition power source this is all done through the Body to Engine Connector (C100).

Cruise Schematics 1 of 2


Cruise 1 of 2 by TheHarley, on Flickr

Cruise Schematics 2 of 2


Cruise 2 of 2 by TheHarley, on Flickr

For the ignition power source simply move the pink wire from pin A9 to pin B4 in the 5.3 harness UBEC C2 connector.

The cruise control switch signal now needs to occupy pins P, B, & S in the C100 connector.  The gray wire for pin P moves from pin L on the engine harness, the dark blue wire at B comes from pin A and the gray wire with a black stripe at Pin S stays where it is.  On the body side the gray wire for pin P comes from the CCM connector pin A.  The dark blue wire for pin B comes from the CCM pin B, and the gray wire with a black stripe at pin S comes from the CCM pin C.

The TAC module also needs a brake switch signal.  I used the CHMSL circuit 1320.  For the engine harness the light blue wire from pin A10 on the 5.3 UBEC connector C2 can be moved to pin F on the C100 connector.  Again on the body side, the light blue wire for the C100 connector pin S comes from the CCM pin G.

Lastly the clutch and stop switch inputs are needed by the TAC module.  For the clutch on the engine side move the gray wire in pin B of C100 to pin K.  On the body side the brown wire with a white stripe already ends at pin K, but also makes a split at the body relay block.  I am planning on cutting out this split and running striaght to pin K.  For my 2000 the other side of the realy block feeds to the CCM and the old PCM input.  The TAC module replaces the need for both of these.

The stop switch is a bit simpler.  On the enigne side move the purple wire from pin C12 in the UBEC C2 Connector to pin E of the C100 connector.  On the body side the stop switch already ends at pin E, so no change is needed.

All of this is documented in the diagrams at the beginnig of this section.