P1351 after replacing ignition coil and icm

[doncaruana]

Sounds like it's time to diagnose that ICM and/or circuit.

Brand new ignition coil and 2nd new ICM (this one is AC Delco) as well as distributor assembly and spark plug wires. I don't think it's the ICM although there might be a funky connection on one of those components.

 

[doncaruana]

If you have the original iCM still, maybe try swapping it back, clear the code, and see if it latches the P1351 again?

I don't and this is 2 new ICMs that throw the code, the current one being AC Delco oem part.

 

[YukonGTmaster]

How does you connector look at your Crankshaft Position Sensor? You started having issues when it was raining. Maybe water ingress into the connector?

 

[exp500]

Loosen the dist hold down bolt. That is your adjuster as explained above. Rotate dist and recheck until it reads 0+- 1 degree above 1000 rpm steady. Tighten hold down! After that then we work on what remains.
Your mechanic made a mistake, not the first guy to do that.
There are a couple fixes if it is still a problem. Ground wire at firewall/ ICM connector bad/corrosion water in computer plug.
Did you notice your Tach bouncing 1-200 rpm?

 

[doncaruana]

Loosen the dist hold down bolt. That is your adjuster as explained above. Rotate dist and recheck until it reads 0+- 1 degree above 1000 rpm steady. Tighten hold down! After that then we work on what remains.
Your mechanic made a mistake, not the first guy to do that.
There are a couple fixes if it is still a problem. Ground wire at firewall/ ICM connector bad/corrosion water in computer plug.
Did you notice your Tach bouncing 1-200 rpm?

Tach was pretty normal. I've got to get the timing addressed and check the connections (at coil, etc) at the same time. It's surely a head scratcher.

 

[east302]

Plus the mechanic said there is no adjustment for this distributor, just like in the screenshot above (which is actually from Mitchell OnDemand) where it says the distributor is installed in a fixed, nonadjustable position for HVS (which I may or may not have??). So, of course, I'm utterly confused...

Some aftermarket distributors come with a fixed hold-down bracket which doesn’t allow the CMP offset to be set. The fix is to swap the hold down with the original one in order to do the replacement correctly. Not sure if you have that one or not.

P1345 is the CMP correlation, as others said it is adjustable on these.

For P1351, the factory manual has the step-by-step diagnostic tables for it. This site has PDFs of them for most years up to 1998:

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

An alternative would be alldatadiy.com which is a subscription site and has the same information (verbatim generally) as the factory manual. They went up in price recently (it’s now around $60/yr) so I let my subscription expire or I would copy the sections for you.

Edit: here is P1351 from the 98 PDF manual…

 

[exp500]

I was not aware of the non adjustable hold down issue, thanks east302.
Using only GM/Delco/Delphi ICM's, Coils, CPS, have fixed the P1351 for my fleet mostly. Also replaced the ICM connector 3 or4 times, CPS connector twice. A few ground issues, repairing firewall grounds was usually it. Twice I have repinned a new white wire from VCM to ICM, on these two I added a ground on VCM. The Tach bouncing is a bad CPS or connector. These are hi mile work trucks all over 200k some over 300k miles. Hope this helps.

 

[east302]

For me, it was a Summit brand distributor that had that issue. While it had aluminum tabs for the cap screws (versus plastic OEM), the hold-down was keyed on there. Some of the reviews suggested that it was for “universal” applications or perhaps the 4.3L, but I couldn’t say for sure.

 

[doncaruana]

I was not aware of the non adjustable hold down issue, thanks east302.
Using only GM/Delco/Delphi ICM's, Coils, CPS, have fixed the P1351 for my fleet mostly. Also replaced the ICM connector 3 or4 times, CPS connector twice. A few ground issues, repairing firewall grounds was usually it. Twice I have repinned a new white wire from VCM to ICM, on these two I added a ground on VCM. The Tach bouncing is a bad CPS or connector. These are hi mile work trucks all over 200k some over 300k miles. Hope this helps.

I took it back over and told him we've got to get the cam retard set regardless and to check the connections while he's at it. Gotta peel the onion and the first layer is that offset.

 

[doncaruana]

Some aftermarket distributors come with a fixed hold-down bracket which doesn’t allow the CMP offset to be set. The fix is to swap the hold down with the original one in order to do the replacement correctly. Not sure if you have that one or not.

P1345 is the CMP correlation, as others said it is adjustable on these.

For P1351, the factory manual has the step-by-step diagnostic tables for it. This site has PDFs of them for most years up to 1998:

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

An alternative would be alldatadiy.com which is a subscription site and has the same information (verbatim generally) as the factory manual. They went up in price recently (it’s now around $60/yr) so I let my subscription expire or I would copy the sections for you.

Edit: here is P1351 from the 98 PDF manual…

View attachment 364567
View attachment 364568
View attachment 364569

Thank you!!

 

[doncaruana]

Really getting frustrated on this...Turns out he only replaced the distributor cap and rotor the first time (after which I got the initial 1351 code). So now he finally replaced the whole distributor (showed me where the gears were worn, blah, blah). Said it never had the start up issue (where it would start, run one second, then stop - which is when it would throw the 1351 code) and started it multiple times in front of me. Said he had adjusted the timing and it was right at zero. I drive it home, pop in my obd reader and start it up and not only does it do the start/stop/start and throw the code, when I look at the cam retard, it's at -8.2 (at about 2800 rpm when I screen capped but it's consistent).

I honestly don't think the guy would lie. Options are a) he lied, b) he did it wrong/didn't get rpm up high enough to set it right, c) it got messed up on the way home.

Mind you, once running, it still seems to work just fine.

What would be the scenario that would make option c happen?

 

[YukonGTmaster]

The Cam Retard Offset should be 0 with a +2 or -2 tolerance above 1000rpm. I set mine at 1500rpm. Not sure about setting it at 2800rpm? Maybe someone else will chime in. Did you verify that the stock distributor hold down bracket was re-installed for distributor adjustability?

 

[exp500]

Scenario/blame matters little because your truck is not fixed.
What is Current status? Is the -8.2 current with no p1345? Which APP are you using? Torque Pro? There are a few threads in engine drivetrain about changing a factor in Torque to get a more reliable number. Test also "usually" done 1000-1500 RPM steady. Tighten Distributor.

As it stands you need to make clear what has been done and in what order...All in one place..... So no new distributor....Just a cap and rotor..... Was coil changed? ICM? Delco/Delphi/GM parts? Ground wire to firewall working? Does the P1351 code still pop? See post 26 and 27 again.

 

[doncaruana]

The Cam Retard Offset should be 0 with a +2 or -2 tolerance above 1000rpm. I set mine at 1500rpm. Not sure about setting it at 2800rpm? Maybe someone else will chime in. Did you verify that the stock distributor hold down bracket was re-installed for distributor adjustability?

My basic point was that I made sure I got the rpm over 1000 before checking the number. I know it's supposed to by +/-2 which is why I'm frutsrated. I haven't looked at the hold down yet.

 

[doncaruana]

Scenario/blame matters little because your truck is not fixed.
What is Current status? Is the -8.2 current with no p1345? Which APP are you using? Torque Pro? There are a few threads in engine drivetrain about changing a factor in Torque to get a more reliable number. Test also "usually" done 1000-1500 RPM steady. Tighten Distributor.

As it stands you need to make clear what has been done and in what order...All in one place..... So no new distributor....Just a cap and rotor..... Was coil changed? ICM? Delco/Delphi/GM parts? Ground wire to firewall working? Does the P1351 code still pop? See post 26 and 27 again.

I don't care about blame - I'm trying to figure out if it's even possible that the guy had it set at 0 and by the time I checked it after a short drive it was at -8 (it read -13 when I took it in).

So let's take it from the top...
Rainy day, truck would not start - no spark (verified).
Next day, dry, started up. I've read that some of the ignition stuff on these can start to cause issues over time, so I took it in to a local mechanic that I've been using for years. He said it was the distributor, I told him to change the ignition coil and ICM also. At this point, he changed the cap, rotor, spark plug wires, ignition coil, and ICM. I don't know what brand the cap & rotor are but the rest are autozone duralast I'm told.
This is when I start getting P1351. Start it, stalls after a second, starts next time, runs fine. Most times it starts with no issue, but every time it does one of these 1 second stalls, it throws P1351. I take him an AC Delco ICM and we swap it out, but this doesn't change anything.
At this point, I get a recommendation from this board for the BAFX OBD plug in (https://www.amazon.com/gp/product/B005NLQAHS) and I'm using DashCommand with it. That's where I got the cam retard readings from and it tells me that it's at -13.
I take it back to the mechanic and tell him it looks like the cam retard is off. This time he replaced the entire distributor, which apparently is from Autozone but keeps the new cap/rotor he originally did the replacement with (I don't know why - the first cap/rotor were higher quality supposedly?) He tells me that now he's getting a P1345 and he's going to set the timing but that that he's not getting P1351 anymore.
I pick it up and he's resolved the P1345 and he shows me it starts normally multiple times, tells me he set it "right at 0 degrees", and shows me there are no codes. I drive home, grab said OBD reader and pop it in. Try to start the truck and get the insta-stall, followed by normal startup. Using DashCommand I see the P1351 code again and the offset at -8 degrees (but no P1345)

I'm tired of taking it back and forth to this guy, despite the fact that I like him and he's done good work in the past. So I'm wondering if maybe I should dive in and try to make the adjustment myself (presuming the correct hold down is there) or if there is some weird scenario where the offset would change by 8 degrees after a short drive.

 

[east302]

To me, the CMP and the P1351 may not necessarily be related. Had the distributor ever been out of the vehicle prior to this? When were the lower intake gaskets replaced? Meaning - it could have been off for some time and you’re only just now noticing it.

If you have a multimeter, I’d suggest going through that GM diagnostic table for the P1351. While there, you can set the CMP to zero. Turn the distributor until the tab for the cap screw is nearly hitting the upper intake. Looking from the front, that tab is on the left and the distributor wiring connector on the upper right. That’s pretty close to zero for starters and then fine tune it.

 

[doncaruana]

To me, the CMP and the P1351 may not necessarily be related. Had the distributor ever been out of the vehicle prior to this? When were the lower intake gaskets replaced? Meaning - it could have been off for some time and you’re only just now noticing it.

If you have a multimeter, I’d suggest going through that GM diagnostic table for the P1351. While there, you can set the CMP to zero. Turn the distributor until the tab for the cap screw is nearly hitting the upper intake. Looking from the front, that tab is on the left and the distributor wiring connector on the upper right. That’s pretty close to zero for starters and then fine tune it.

Not sure they're related either. Just layers of an onion at this point. I do not ever recall the distributor being out specifically but the I believe the lower intake gaskets were done some time ago (not sure about this either).

I've got a meter.

 

[YukonGTmaster]

I had the dreaded P1345. When I set my distributor, this was the initial at Top Dead Center. At 1500rpm, I had to rotate it counter clockwise until the ear where the screw for the cap goes into the distributor, was actually contacting the upper intake. I was told by the forum dudes that that was normal. I think I got mine to -0.3 at 1500rpm. Have a look back there and see if that distributor is rotated near to touching the upper intake.

 

[doncaruana]

I had the dreaded P1345. When I set my distributor, this was the initial at Top Dead Center. At 1500rpm, I had to rotate it counter clockwise until the ear where the screw for the cap goes into the distributor, was actually contacting the upper intake. I was told by the forum dudes that that was normal. I think I got mine to -0.3 at 1500rpm. Have a look back there and see if that distributor is rotated near to touching the upper intake.

Actually the P1345 is gone... I'm back to 1351

 

[YukonGTmaster]

Actually the P1345 is gone... I'm back to 1351

Oh man!