95 SC throwing codes - intermittent running problems

Hi all,
Been trying to figure out what is going on with my 95... been having problems with intermittent chugging up hills and rough running.

a few days ago I finally got the DTCs out of my car:

P0321 - Ignition/Distributor Engine Speed Input Circuit Range/Performance
- Ignition System Problem, 18X Interrupts Lost Signal

P0341 - Camshaft Position Sensor Circuit Range/Performance

P0361 - Ignition Coil K Primary/Secondary Circuit Malfunction
- Ignition System Problem, Electric Spark Timing, EST Not Toggling

P0670 - Glow Plug control circuit error
- Quad Driver Module, QDM 4 Fault

I replaced the center and rear coils on the car and inspected the wiring.
The harness that feeds the oil pressure, crank & cam sensors had the outer protective shielding (the corrugated stuff) melted away but I closely inspected the wires and they were all completely fine (no discoloration, wires were flexible, no indication of damage).
I then inspected the firewall wiring and primary connectors and all looked fine (no corrosion at all)
Finally, I inspected the PCM (under the glove box) ... the blue connector seemed a little looser than the other 2 connectors. I disconnected the battery and removed the PCM (A rebuilt one by the way). Plugged everything back in and drove the car. It ran fine.

I have recently replaced the plugs and wires. the wires were not AC delco ( a mechanic sold them to me)

today I get in to use the car for work (havent been driving it lately) and the CEL was on. the next time I started it the "traction off" and the CEL were on. the next time I started both were off. car was running fine today with no sputtering or chugging.

took the car to autozone and re-read the codes and got the following:

P0670
P0321
P0361
P0670 (yes it came in twice)

I cleared the codes and came directly home to make this post.

the one code that didnt come up again is the cam sensor code (P0341).

Im thinking the cheapo PCM is going bad or maybe the ignition control module is failing.... any ideas? the chugging and sputtering seems to occur when Im driving up a hill after the car has been running for a while.

thanks for any ideas/input.

Jeff

Did you ever replace the front coil, or at least test it? You've replaced the plugs and wires, but this still seems like an ignition problem, or at least partly so.

I think the P0341 - Camshaft Position Sensor code starts out as random occurance, then gets more frequent. Keep an eye out for that one again.

How many miles on the engine? When & why was the PCM replaced?

143K... I didnt know the PCM was replaced. had the car for a year.

I checked the front coil by unplugging the coil wire and got the zap of my life... the coil seemed strong. the rear one had failed so it got replaced, then i bought and put in the center one just for laughs.

I was under the impression that coils just die and dont really give any warning (thats what happened to the rear one).

thanks AA

Jeff

P0321 Spark Reference Circuit - PCM Controlled
P1670 QDM #4 - PCM Controlled
P1350/1351 IC Circuit - PCM Controlled

When you said you disconnected the battery and messed with that plug on the PCM, you reset the codes. They came back......all of these codes are related to PCM circuits. Sounds like that PCM may be the culprit. I don't see how all of those codes could be thrown at once with a simple wiring problem, being that they (components) have nothing in common except the PCM.

The P1351 (P0351) sets when the IC circuit is grounded at startup (through the PCM)

P0321 sets when the PCM detects 50 crank revolutions and no spark reference pulses. (during startup only, spark reference is used to improve ignition timing up to 1200rpm's)

P1670 (P0670). In this case, the PCM controls the A/C Relay, Low Speed Fan Relay, High Speed Fan Relay, and the Series/Parallel Cooling Fan Relay (hence QUAD Driver Circuit). This QDM supplies the ground for all of these through the PCM.

In a nutshell, all of these are controlled/commanded by the PCM. It's possible that a ground driver within the PCM has taken a dump. Make sure and check that the PCM case has a good ground.

Hope it helps......

thanks abaddon

The PCM was in a plastic clip holder and not screwed into any gound. I didnt see a ground wire coming off of it ( I was looking for it from my readings here).

Is the PCM ground cable under the dash in that general area?

thanks

Jeff,

Coils don't just die. I am still running all three OEM coils at 205k miles, and I plan to run them for another 100k.

They die for a very specific reason: unmaintained plugs and wires. I bet the old ones were trashed. If the other two packs went bad, something caused that. There is good reason to properly test or replace the front coil pack. It may have shocked you, but this is a very high energy coil that puts out much hotter spark under load. You can't assume the coil will perform under boost, when there is more demand.

I wouldn't replace it just yet, but if you troubleshoot the PCM, wiring, and Cam Position Sensor with no luck, maybe try replacing the coil.

OK will do.

so I should not bother with the ignition control module and concentrate more on the PCM at this point?

jeffyd123 wrote:

OK will do.

so I should not bother with the ignition control module and concentrate more on the PCM at this point?

Considering that the IC is controlled by the PCM, on all levels.....

There is a way we (you) can test all the wires between the PCM and the IC. It requires an Ohmmeter, some extra wire to reach from the IC to the PCM, and the proper test terminal for the PCM connector (so you don't damage the terminals).

do i find the test terminal online somewhere?

jeffyd123 wrote:

do i find the test terminal online somewhere?

Eh, it's not something to buy one of. Usually comes in a kit with a bunch of different kinds. You can still do it without, I was merely suggesting the "proper" way to do it. Using the terminal adapters just lets you probe into the connectors without damaging them. If your confident you can do it without damaging them (I don't know your mechanical/electrical backround), have at it. If you want to tackle it, I will post which wires/terminals to test for you, and possibly the schematic.

jeffyd123 wrote:

I disconnected the battery and removed the PCM (A rebuilt one by the way). Plugged everything back in and drove the car. It ran fine.

Sounds to me like the problem is under the dash...

just got done reading the series II post about camshaft sensors (my eyes are bleeding!). Looks like there are quite a few failures of the wires between the ICM > CPS... ICM > firewall plug... firewall plug > PCM.

As far as testing the plugs... is it OK to use a carefully inserted paperclip to make contact in the plug or maybe insert a lead in the backside (where the wires are) of the plug?

The schematic and/or terminal layout would be a good help...Im not sure if the ones on the series II thread are correct for my 95.

thanks eldo

jeff

Here is the schematic for P0321



The schematic for P1670



The schematic for P1350/1351



On the top schematic (P0321), the wire you want to pay most attention to is the SPARK REFERENCE (647 LT BLU/BLACK). That's the wire that "sets" P0321.

On the center schematic (P1670), I'd start by checking the fuses. Actually, I'd probably save that one for last if needed......

On the lowest schematic (P1350/1351), you need to check the BYPASS (424 TAN/BLACK) wire between the PCM and the IC. Also check the IGNITION CONTROL (423 WHT) circuit.

I would check all of those wires for shorts to ground (you should have no continuity between any of those wires and ground), and also resistance (PCM to component). I did notice 1 other thing that these codes have in common besides the PCM and ICM.....The 8-WAY IGNITION JUMPER HARNESS CONNECTOR houses all the wires from the top and bottom schematics, although it is not shown in the bottom schematic?!

Hope it helps.....I also have flow charts if you need......

abaddon... you are da MAN! thanks!

I was digging under the hood today checking wires:

the wires leading from the ICM (along the front of the engine) are fully exposed! the plastic corrugated conduit is completely gone. There is oil all over the wires and I had a water leak there last year from the "S" hose that goes into the water pump.

I couldnt get the wires out without some dissassembly of the ICM mount but Im tearing into it soon. the wires i did see looked intact.

And of course I drive the car today... get about 2 miles down the road... it starts to sputter and stalls out. It started right back up and I limped it home. will pull the codes ASAP.

thanks again

Jeff

Np man. Now that I look at it again, you can test all the wires you need from that 8-way connector at the ICM (to the PCM). A, B, and C are it.

Now that you mention the harness was rubbed through, oil on them, and had a coolant leak there, I wouldn't be surprised if those wires are corroded/broken. Even if the insulation is still there, the smallest hole or cut can cause the internal copper to corrode. I've chased down quite a few bad wires where everything looked "good", only to find the copper broken inside.....

ya under closer inspection of the ICM wires it looked like someone had been probing the wires. i noticed a very small hole in the black wire.

god help me...

Oh well... some day my car will run great again. the engine and tranny are still solid as hell.

hey BTW is there anyone that sells the under-hood wiring harness for these cars?

jeffyd123 wrote:

ya under closer inspection of the ICM wires it looked like someone had been probing the wires. i noticed a very small hole in the black wire.

god help me...

Oh well... some day my car will run great again. the engine and tranny are still solid as hell.

hey BTW is there anyone that sells the under-hood wiring harness for these cars?

I think you can have one made. Check:

http://www.keepitcleanwiring.com

for a kit.

Less expensive: I think you can get enough of the wiring kit to splice/fix it. Ask the auto shop teacher at a trade school that teaches auto mechanics for suggestions on where to get/how much to pay for kit.

Less expensive still: contact Ed Morad (http://moradpartscompany.com) he can tell you if he's getting one in and can pull the wiring (or if you are close enough you can offer to go to Eds and pull it).

What I would do: I'd look into getting a wiring repair kit off EBay from one or another of the sellers that is liquidating closed car dealers about now.

Albertj

If you determine that those wires are the problem, the wire repair kit (ICM harness) would be perfect. I'd check with Morad first. Just send 'em an email describing what you need (ICM harness). They reply very fast.

Don't try to "patch" the wires. That bend in the harness at the ICM doesn't have enough space to house crimp connectors or scotch locks. Yes, you can do it that way, but you will be adding even more stress to that bend. Get the new (or used) harness and splice it in about a foot down where it's straight and there's room (if that's the problem).

Thanks for the link Alby!

holy shit! Morad has the entire engine bay harness in stock!

Im gonna call him. for $150 thats not too bad of a deal (Id like it more if it was $50 tho LOL)

you guys are geniuses.

BTW... is this a very tough job to replace the entire harness... from what i can see , looks like about 6 hours or so.

My thinking (and tell me if you think its stupid) is if I replace with a known good harness (after reading about all the bad harnesses out there) that if its a part, then I can confidently start putting parts in...right?

well i ordered it so it can be here by the weekend and Ill throw it in there and see what happens.

I wouldn't replace the entire harness just yet, unless of course you know that there are other bad spots. I would just cut and splice the part you need for now, and save the rest for later. It's a lot of work to replace the whole thing....but if that's what you wanna do, have at it

Are we sure that's what the problem is for sure? (the wires)......

no im not sure... I did fiddle with the wires by the "S" coolant hose at the front of the engine and when i drove the car it stalled about 2 miles later. The car has issues but never stalls.

Plus Im thinking Im going to change the belts and camshaft sensor while everything is apart.

I figure when i get the harness done, if i still have problems I can then throw parts at it and feel confident that my wiring is OK.... hopefully.

the guys at morad said they start the car and let it run for 15 minutes before they disassemble them and they dont have any CEL... thats what they said so hopefully Ill get a good harness. Ill inspect it closely before i install it and most likely re-wrap the conduit for some extra protection.

Thanks for the great info. I have a question:

When I have the belts off... can i inspect the camshaft sensor magnet without removing the front case. Is there an inspection port like on the series II?

Im thinking I will try to re-route the harness where it gets smashed between the ICM mount and water pump... the harness is crushed in there.then it get squeezed again between the head and where the "S" hose goes into the water pump.

Im thinking about trying to run it so it has a half-inch of clearance so it isnt sitting directly on the head to prevent future melting.

Ugh.. another weekend under my car.

jeffyd123 wrote:

no im not sure... I did fiddle with the wires by the "S" coolant hose at the front of the engine and when i drove the car it stalled about 2 miles later. The car has issues but never stalls.

Plus Im thinking Im going to change the belts and camshaft sensor while everything is apart.

I figure when i get the harness done, if i still have problems I can then throw parts at it and feel confident that my wiring is OK.... hopefully.

the guys at morad said they start the car and let it run for 15 minutes before they disassemble them and they dont have any CEL... thats what they said so hopefully Ill get a good harness. Ill inspect it closely before i install it and most likely re-wrap the conduit for some extra protection.

Thanks for the great info. I have a question:

When I have the belts off... can i inspect the camshaft sensor magnet without removing the front case. Is there an inspection port like on the series II?

Ed's always been decent and fair.

As for "put parts in" my only comment is, "first things first." Meaning first you get the apparent problem fixed. You can see the physical damage to the wiring harness. So repair/replace it. Then find and fix the other problems. By the way be sure to check the wires in that replacement harness for continuity through the firewall connector - that's a known problem area and way easier to fix on the bench rather than in the car.

If the wrap on the replacement harness is good I would not bother changing it. I would consider getting some *very* good electrical tape (it's like $4/roll at Home Depot rather than 2 rolls for a $1 at the dollar store). You can then rewrap where the OE wrap has come loose. Whatever you do, don't use the cheapie electrical tape for an under-hood application, it won't last.

As for the cam sensor magnet, you don't need to pull the belts to get at the cam sensor but small hands will help. You can see what you can see through that little hole. I do not know of anyone on this site that has had a cam sensor magnet problem but hopefully one of the mechanics will comment. I would not be worrying about that one now, either, unless there was some physical damage in that part of the car.

If your riv has 75 to 150 thousand miles and you have not replaced the *crank* snesor however, you may need to. I can not say whether most of the people with high milage Rivs have - but it's one of the few problems that many people with the 3800 engine have had. You should get a special puller to get the harmonic balancer off (the crank sensor sits behind the HB) if that is the issue. A mech can replace it for under $200, My local GM dealer charged me less than that (thank goodness). They replaced it twice. Once when it failed the first time and again when the lo-price unit they installed crapped out 2 years later - that time they put in a Delphi, I don't think I will hear from it again.

Albertj

albertj wrote:

I would consider getting some *very* good electrical tape (it's like $4/roll at Home Depot rather than 2 rolls for a $1 at the dollar store).

As for the cam sensor magnet, you don't need to pull the belts to get at the cam sensor but small hands will help. You can see what you can see through that little hole. I do not know of anyone on this site that has had a cam sensor magnet problem but hopefully one of the mechanics will comment. I would not be worrying about that one now, either, unless there was some physical damage in that part of the car.

If your riv has 75 to 150 thousand miles and you have not replaced the *crank* snesor however, you may need to.

Albertj

AGREED on good electrical tape.

NEVER seen/had a problem with a Cam Sensor Magnet.....yet

YES, replace the Crank Sensor if you in there anyway, and it hasn't been changed. Mine went at 90k.

I just bought an Eichlin Crank Position Sensor from NAPA for $46.00.