I'm stumped...truck no worky.

[pmkls1]

It sounds like a wiring issue I agree, but the pcm still has to ground the injectors while cranking. Considering the fact that you can't communicate with the pcm along with the other symptoms, it sounds like there is a faulty power or ground circuit for the pcm. It also sounds like this problem began before the new TB was installed although I would still check the 5v reference circuits with the sensors unplugged. I can't get to a good wiring diagram at the moment, but considering all present symptoms it points to something pcm related like wiring, fuses, relays, terminals, ignition switch, etc...... Since the ignition operates in bypass mode during cranking it should still have spark while cranking.

[907 Chevy]

I can get a noid light at one of the local parts stores, I'll see about getting one today.

When I jumped the injectors no fuel came out, but there was no pressure in the system when I jumped them. I had considered a fuel delivery issue as well, but fuel pressure is right where I set it, which tells me that fuel is reaching the regulator just fine...right?

I'll check PCM ref voltages after work today and while I'm at it, I'm just going to start over and recheck everything...grounds, fuses, etc etc.

Thanks for all the help guys.

[907 Chevy]

Alright, just a quick update: I picked up a noid light at lunch and ran home to check things out...the PCM is not commanding the injectors to fire. I was already pretty positive that was the case, but it's good to make sure in any case.

I didn't have time to test anything else, but will get to it tonight after work...

[davo727]

My buddys truck did this with a new harness and I found that the TPS wiring was backwards and the PCM thinks its at full throttle like you are trying to clear a flooded condition therefore wont fire the injectors. Corrected tps wiring and started right up.

[907 Chevy]

Yeah, I thought that maybe I screwed up wiring the TPS connector, but everything looks fine and tested within normal range.

Alright, I'm going to try to be as detailed as possible...I tested everything again and here's what I came up with...

Red Connector
Pin
A1- Blk/Wht System ground...good continuity with bat-
A2- Tan/Wht System Ground...good continuity with bat-
A9- Drk Grn Inj2 control...supposed to be nominal system voltage of between 12-14volts. Measured 12.5v
A15- Drk Blu TPS Signal...measured 0.87v closed throttle. Not ideal, but is close enough to not be a problem I think.
A16- Drk Blu Inj1 Control...supposed to be nominal system voltage between 12-14volts. Measured 12.5v

B3- Blk Sensor Ground...good continuity with bat-
B4- Blk Sensor Ground...good continuity with bat-

Blue Connector
Pin
E15- Pink Ignition Feed...supposed to be nominal system voltage of between 12-14volts. Measured in range
E16 Orn Ignition Feed...supposed to be nominal system voltage between 12-14volts. Measured in range
E14 MAP Ref...supposed to read around 5v. Measured 5.05v

F9- Tan Serial Data...supposed to read around 5v...measured 3.42v. Is that too low?
F14- Gray TPS Ref...supposed to read around 5v...measured almost exactly that
F15 Pink Ignition Feed...was not found in my harness...?? Not sure if this is important or not?

I guess tomorrow I'll pull the dizzy cap and make sure I have the pickup coil plugged into the ICM even though I know I do and recheck all connections for the tenth time, hoping I've missed something obvious that's been staring me in the face.

Thoughts? I'm almost out of ideas...could the injector drivers be burned up in both of the PCM's I have? Do I have two PCM's that are toast?

[chevmasta]

can you pour some fuel down the intake and will it start and run?

[907 Chevy]

can you pour some fuel down the intake and will it start and run?

I shot some starting fluid into the intake manifold and the engine made an attempt to start, well it coughed a little bit at least. Lol

[jim_in_dorris]

Wha about pins A4 (IC REF HIGH ppl/wht) and A5(IC REF LOW red/blk) from the distributor? they provide DRP without which your truck might not start?

[davo727]

In the first post you said it wouldnt start before the work you did. I would put a brand new dist module in it or pull one out of a truck that you know works and try that.

[EagleMark]

F15 Pink Ignition Feed...was not found in my harness...?? Not sure if this is important or not?

and there's your sign!

[PJG1173]

I assume it ran before you swapped the intake? if so its hard to imagine that the wire at F15 got up and ran away with the old intake.

[907 Chevy]

I assume it ran before you swapped the intake? if so its hard to imagine that the wire at F15 got up and ran away with the old intake.

and there's your sign!

Yeah it ran before I swapped the intake, although it did refuse to start the last couple times I attempted to start it before swapping the intake. I can't imagine that wire ran away either, I did clean up the harness some, but only removed wires and terminals for the auto transmission that's no longer there and that wasn't recently. Perhaps F15 isn't used??

In the first post you said it wouldnt start before the work you did. I would put a brand new dist module in it or pull one out of a truck that you know works and try that.

I swapped in an ICM that was known good, or so I thought. At this point, the ICM is the only thing that remains untested and I made a huge assumption in believing the ICM I used was still good.

What about pins A4 (IC REF HIGH ppl/wht) and A5(IC REF LOW red/blk) from the distributor? they provide DRP without which your truck might not start?

I haven't tested IC Ref High and Low because I haven't had anyone there to crank the engine for me while I check for DRP.

My game plan at this point is to have my buddy come over tonight and crank the engine for me while I check for DRP at those IC Ref pins...if I'm not getting DRP, the only culprit can be either the ICM, or a break in the wiring(very unlikely). If I am getting DRP, that points to a bad PCM, yes?

[PJG1173]

Yeah it ran before I swapped the intake, although it did refuse to start the last couple times I attempted to start it before swapping the intake. I can't imagine that wire ran away either, I did clean up the harness some, but only removed wires and terminals for the auto transmission that's no longer there and that wasn't recently. Perhaps F15 isn't used??

when I made the custom wire harness for my toyota I do recall having to have both F15 and E15 connected to switched power. one of the two (don't recall which) is connected to the same fuse as the injectors. the other is connected to the egr. easy test is to jump the two pins together so they both get ignition power.

[helo]

REALLY check your 5v wires? 7427/8625 pins A14, B2, E14, F9, F14 (others??)

5v is used for TPS & map (duh), but also for OBD and ICM !!!!

Something that probably doesn't matter, but I've been wondering about...I relocated the ignition coil to the fire wall, does the coil need to be grounded to the engine to work?

Hmm? More important, the ICM __MUST__ have good ground. This is a huge shortcoming with factory setup, because ground comes from intake manifold through the distributor hold-down clip, to ICM mounted to distributor base. Overkill fix is drill 1/4" hole in dizzy base and run a ground wire with ring terminals, super-overkill is relocate ICM onto grounded heatsink and splice the pickup coil wires & coil wiring to reach..

To me, this sounds like your pickup coil signal is not making it to ICM, or ICM is not sending the 5v square wave signal to PCM (because ICM does not have GND or 5v), so PCM never knows engine is turning. Not connecting via OBD seems odd, though..
I expect some sort of issue with the 5v wires.

[907 Chevy]

REALLY check your 5v wires? 7427/8625 pins A14, B2, E14, F9, F14 (others??)

5v is used for TPS & map (duh), but also for OBD and ICM !!!!




Hmm? More important, the ICM __MUST__ have good ground. This is a huge shortcoming with factory setup, because ground comes from intake manifold through the distributor hold-down clip, to ICM mounted to distributor base. Overkill fix is drill 1/4" hole in dizzy base and run a ground wire with ring terminals, super-overkill is relocate ICM onto grounded heatsink and splice the pickup coil wires & coil wiring to reach..

To me, this sounds like your pickup coil signal is not making it to ICM, or ICM is not sending the 5v square wave signal to PCM (because ICM does not have GND or 5v), so PCM never knows engine is turning. Not connecting via OBD seems odd, though..
I expect some sort of issue with the 5v wires.

You raise a good point about the crappy design for grounding the ICM. I checked for voltage at pin A5 IC Ref High as jim_in_dorris suggested while my friend cranked the engine over and got no voltage to that pin. The troubleshooting chart in the link Mark provided says I should be getting around 1.2v with engine running.
So the PCM has no idea that the engine is turning over because it's receiving no signal from the ICM. If that's the case, then I'm looking at an ICM that isn't properly grounded or the ICM itself has failed. I gotta leave town for work for a couple days, but will check continuity between the distributor base and ground when I get back and add a ground wire to the dizzy if needed, as well as have the ICM tested.

when I made the custom wire harness for my toyota I do recall having to have both F15 and E15 connected to switched power. one of the two (don't recall which) is connected to the same fuse as the injectors. the other is connected to the egr. easy test is to jump the two pins together so they both get ignition power.

I'll try that, although I'm wondering why the PCM would need two 12v ignition sources? It seems more than a little redundant...hmm