Ok, I need some help as I can’t figure out what’s going on.

My engine is a 2004 5.3 with LS1 injectors, Intake, coils and DBC throttle body.

The PCM is a 2004 express Van tune with the blue / green connectors.

I have fuel and spark but no injector pulse. I’m unsure where to look at this point. I have power at the injector on the 12v side but the noid light isn’t lighting up when I crank the motor.

Keep in mind this engine was running fine before I decided to move the PCM inside the car to clean up the engine bay. It has vats delete already in the programming and nothing has been changed there.

I re-wired and rebuilt my harness by shortening wires and added new wiring for most of the wiring. I meticulously labeled everything and doubled checked twice before inserting wire into pcm connector.

I also over-grounded the harness by putting ground terminals for inside the car and back of the engine head. Everything soldered and goes to each point. I also added grounds from the motor to firewall and motor to frame. Battery ground is on the engine block.

Here’s what I have done so far:

• Verified spark with a spark plug ignition tool (It lights up when cranking

• Verified fuel pressure with a gauge on the fuel rail @ 58lbs. Fuel squirted out of the rail and you can hear the pump priming when turning the key switch on.

• Verified 12 volts on the pcm and sensor circuits when cranking

• Verified motor will actually run by squirting starter fluid inside the throttle body

• Checked all grounds, including back of the head and inside the car.

• Pulled codes with a reader, at first I got a P0107 with meant issues with map sensor. I pulled the plug and checked 5v reference and low reference on the terminals..both were good so I put the plug back in. Cleared codes and checked again. Check engine light is still on but no codes now. I’m guessing the plug was partially out of the map sensor or something.

• I checked PCM grounds on terminals blue connector 1, 24, 27, 40, 64, 67 and green connector 1 and 40…..all were good.

• Battery has a full charge

• Checked fuses on my main fuse block for the harness, all good.

What can cause the injectors not to pulse? I was monkeying around with it for a split second last night and got it to work for one start cycle.

The noid light was working too. But for some reason it quit and I can’t duplicate it.

I need to check the wiring at the crank and camshaft sensor next but I am running out of ideas and the fact that I am not getting codes for either is making me less than optimistic about it.

I just don’t know why the check engine light is on.

It’s got to be something simple, I would appreciate any suggestions I can get.

I've got this listed on a few sites as I am off right now and would like to keep moving forward on this and get it going.

Thanks in advance

 

I'm going through and checking everything.

I checked for power on the camshaft position sensor plug and I have 12v reference on the red wire and low reference on the pink/black wire like I am supposed to.

I was under the impression that the camshaft position sensor controls injector pulse so I def wanted to check that. So I am getting power and ground to that from the PCM.

 

I think you have your answer right there. Usually when something goes wrong with my cars, its something I created. The problem started when you rewired the car. I would be looking at what I did to the car last. More often then not, its my own fault.

Do you have HP Tuners VCM Scanner?

 

I do, I just fired it up and pulled DTC's and I got a little more info than the cheap code reader I have

[] P0107 - Manifold Absolute Pressure/BARO Sensor Low (SES) (Old) (History) (Current) (Immature)

[] P0315 - Crankshaft Position System Variation Not Learned (SES) (Old) (History) (Current) (Immature)

[] P1637 - Generator L-Terminal Circuit (Old) (History) (Current) (Immature)

Code P0315 has me the most curious as that could be why the injectors aren't firing

I don't understand what the notes in parentheses mean though

 

From what I understand of the notes in the parenthesis mean:

• History - happened in the past, but hasn't happened for enough drive cycles to self clear.
• Current - fairly obvious this one.
• Immature - happened enough to report, but may have not happened enough to trigger the service engine soon light, or is commanded to not trigger the light
• SES - triggers the service engine soon light

 

Thanks, that clears it up.

I was going over my codes and code P1637 (generator L terminal circuit) is because I left the exciter wire out of my harness on purpose.

I have an ignition switched wire coming off my AAW fuse box (underhood side) that is specifically for alternators. I have a resistor wired inline to allow the alternator to charge.

Would that cause a no start condition? Can I delete the exciter wire request out of the PCM through HPtuners? (EDIT: I'll turn off the reporting for that code)

 

I was leaning towards a bad crank sensor, but it was working fine before the harness re-work. I have verified all the wiring to it and I am getting rpm when cranking it so the crank sensor is probably fine.

I'm going to have to do some research on what these values mean as this is a learning process for me...this was during a crank cycle...the car never started

 

Did you check the wiring from injectors to PCM...?

 

Yeah I checked those for continuity too. All checked out. It was working fine for one crank cycle last night but I am unsure what I did and can't duplicate it. It's a headache trying to figure this out as it seems like I have checked all of the things to check when these symptoms show up

 

Are the terminal pins inside the connectors making contact...?

Is the PCM missing a ground...?

 

Yeah I double checked that terminal pins, they are seated correctly and nothing is bent. I even took out the rubber seals to allow them to seat a little tighter.

PCM grounds are all good, I ran multiple grounding points throughout the harness all to the same grounds, two attach to the back of the heads and one inside the dash on the firewall. Ring terminals are crimped and soldered.

My PCM is grounded on Blue connector pins 1, 24, 27, 40, 64, 67 and green connector 1 and 40. All tested and working.

I also have ground straps coming off the same spot on the back of the head to firewall and frame. Battery is grounded to the motor.

 

Someone mentioned my TPS being at 100% during cranking from my screenshot. Said that could cut the injectors

I went out and unplugged the TPS plug from the throttle body, turn the ign on for 10 seconds then off.

Plugged the connector back into the TPS and it tried to start it and the motor fired for a 1/2 second and cut off...so I think I am in the right area

Now to start testing and troubleshooting those wires, I put a stock throttle body back on the motor this go around, but I may take it off and put on my cheap aftermarket back, which I know works if the wiring and sensor checks out

 

It's ALIVE!

I'm actually kind of embarrassed about this but here is what happened:

I had the TPS low reference and 5v reference wires reversed. At some point a few years ago I removed the DBW throttle body set-up and added a PCM capable and cable throttle body set-up.

But to do this I had to add the specific wires to my 2004 harness which included TPS and IAC valve.

During the process I made notes in my 2004 Harness spreadsheet for Pin 8 and Pin 60 on the blue connector for low reference and 5 volts, only difference is I flipped the wire colors.

I actually installed it this way on my harness before I recently modified it, so it's been this way all along. Makes sense now why I was fighting idle and running issues before taking it to the body shop. All I did was labeled the wires based on my old pin outs and re-installed them the same way on this one.

I went to eficonnections website and looked at their info on the TPS pigtail and compared it to my spreadsheet, the colors were backwards. I pulled a unmodified 2004 GTO pin out list and sure enough it didn't match what I had.

Went and looked at my PCM connectors and I did in fact have them backwards, moved them to the correct spot.

Engine fired right up and didn't miss a lick

Thanks for the help

 

Glad you found it