95 blazer 4x4, 4.3, EDI system, OBD1.5

I keep fixing things, and the same problem keeps coming back! Every time after I replace some parts, the car runs fine around town, but if I take it for a long ride 15 miles or more, it dies while I'm traveling down the road. It gives no warning, just dies! Then it won't start at all, it turns over fine, just won't fire at all! Like it needs spark or gas!

Things I've replaced so far.

Battery and Starter
Spider, Nut Kit, Eletrical Conector to spider, and Fuel filter.
Coil.
Camshaft sensor. ( in distribitor )
Ignition Control Module.
Cap, Rotor, Wires, and Plugs ( all AC Dleco )

Checked the fule pump 10 ways to Sunday!! Key on, 60lbs, key off 55lbs held over 50lbs for more then 10 minutes. At filter, key on 80lbs, held over 65 lbs for 10 minutges.

Checked spark at plug, spark was good, but it was yellow not blue. (but should still try to fire up)

I'm disabled and on a fixed income, I've just about maxed my credit card out on all these parts, some did need to be replaced, but not all, and I can't afford to take it to a shop! This is my only mode of transpertation, I really need some help here!

I've spent hours reading all the simular threads, but no one ever post what the problem was, or how to fix it!

Based on the fact that it has spark and there is plenty of fuel presure, I'm assuming the spider isn't firing. The last time my car died, I pulled off the plenum and checked the conector and made sure that all 6 poppets were spraying gas! So, it must be the signal being sent to the spider to fire. What are all the things that could affect the signal when the car gets hot? Could it have a signal, but if it's weak, would that not open the spider?

I read somewhere about disconecting the battery for 10 minutes, but I don't know what they were refering to. Does that reset the PCM, or a sticky relay and allow the car to work untill it heats up again?

Thanks everyone, I hope someone out here knows the answer!!!!!

If this has happened to you, please post what you did to fix it!!! PLEASE HELP!!!!

 

OK, The car has been sitting few a few days, because I havn't got any responces, and I don't know what to do at this point! Just for shoots and giggles, I tryed to start it today, and boom it started right up! The only thing I did, was disconect the battery for about 10 minutes a few days ago. But after I reconected the battery, the car still wouldn't start. The only thing I can think of, is that when the car sat for a few days it cooled down and the problem went away. I'm afraid to drive it, because I know as soon as it heats up again it will die and leave me stuck somewhere.

Has anyone out there had this problem before, and what can cause it to shut down when it gets hot, and start up when it cools back down? can the CPS cause this?

 

Just like I thought! I took the car for a ride and boom 5 miles down the road it dies on the freeway! Had to have it towed home!!

I was able to borrow a scanner that would work on my OBD 1.5 It was an Innova 3100 for anyone looking for a scanner.

The code that came up, was.

P1351 and it read.

1. IC circuit High Voltage

2. circuits 1 & 4 malfunction

Does anyone know what this means? When it refers to circuits 1 & 4, what circuits does it mean? (what part is the circuit from?)

 

"IC" = Ignition controller. That's the module on the bracket with the coil.

BTW, yours should work with any Generic OBD-II reader or scan tool. If the tool wants to know year, make and model, just tell the tool you have a 1996 model. I'm guessing that you have the PCM on the coolant recovery tank. I'm fairly certain that those are all wired on pin 2 of the DLC for J1850 data.

I've kind of made a hobby out of figuring out what was out there in 1995. There's a lot of misinformation about that year for GM vehicles. If you don't mind answering a few questions, I"m curious:

When was yours made? (month and year from the door jamb sticker) Where was it made? (VIN position 11, after th "S" for 1995 model year and before the last 6 digits serial number) Does the emissions label say "OBD II Certified"?

 

I've tryed several readers on it and none have worked untill this one, but I have to give it back!

Ok, i'll answer your questions first.
MADE IN: 02-1995 From: the number 2 follows the S in the Vin.
The hood was replaced befor I bought it, so it has no emissions label, but the PCM is over the coolant tank and it has the OBD II port for the reader.

I replaced the coil and the ICM, so those are not the problem.
Do you know where the 1 and 4 circuits are located?
Could the altanator, voltage regulator, or the compassitor cause this problem by releasing to much voltage?

 

The words "new" and "good" are two entirely different words with different meanings. It's possible that the P1351 DTC is an old code that came when the ICM and/or coil were bad before, and that it has nothing to do with the current problem. I'm very skeptical, but that might be possible.

Clear your codes (either with the scan tool, or disconnect the battery for 10 minutes or so), buy some "keyboard duster"/"electronics duster"/"canned air" and carry that with you for diagnostic testing the next time it dies. Also carry a volt/ohm meter to test things while it's failing.

Here's how the ignition controller/ignition coil works on this engine. The PCM sends a pulse down the "Electronic Spark Timing" wire to the ignition controller. It then monitors the voltage on that wire. The ignition controller is supposed to switch a high current switching transistor which provides a ground path for the coil, and also grounds the EST wire from the PCM. If the PCM doesn't see ground on that wire, but instead measures a voltage above about 5 volts when it should be grounded, it sets DTC 1351.

The "Circuit 1-4" stuff is indicating the first coil. On a V6 with a distributorless system, there are three coils, and DTCP 1351 indicates a problem on the coil for cylinders 1 and 4. On those systems, P1352 is for the second ignition coil circuit, and P1353 is for the third ignition coil circuit. On this engine, there's only one coil, so that's not really applicable.

There are very few things that can cause a P1351 DTC. The most likely are:

• Bad ignition module, sometimes intermittent, "bad when hot"
• Bad coil (low resistance), sometimes intermittent, "bad when hot"
• Bad ground at the ignition module connector, this is usually permanent, quits and won't restart, very rarely "bad when hot" intermittent
• Bad wiring between ignition module and PCM (not very likely, but possible), also more likely to be a permanent condition.

You can measure the coil resistance when it's failing. Carry your volt/ohm meter and check it while it's still hot. Turn off the key, pull the low voltage connector at the coil and measure from the pin on the coil for the pink wire to to the pin on the coil,for the white wire. IIRC, that's the end wires on the connector. The resistance there should be 0.2 ohms to 0.5 ohms for yours, I think. The early 1995's with the ECM behind the dash are 0.3 ohms to 1.3 ohms. If the coil is shorted (less than 0.2 ohms) when hot, that's your problem.

You can check the resistance to ground at the black wire on the ignition module. It should be <0.1 ohms (less than 0.01 ohms is even better) to ground from the connector pin on the black wire. Again, a bad ground here usually causes no-start, permanent failure until fixed, so I doubt this is an issue on yours.

If you're stopped on the side of the road, you might get it restarted by cooling the failing part(s). Try cooling the ignition module first. Use "canned air" or "keyboard/electronics duster." Turn the can upside down and carefully spray the liquid on the ignition module. The liquid is super cold, and it will boil away and cool whatever it touches. Be careful not to get of the liquid any on your skin, it can cause frostbite. After cooling the ignition module, try starting it. If it starts, you have a bad module. If it still doesn't start, use the liquid from the duster can to cool the ignition coil next. When it's intermittent after driving a while, usually cooling those two parts will get it to start again for a short time. If cooling the coil "fixes" the problem, the next time it stops, cool the coil first. If cooling just the coil fixes it, it's just the coil. If it only restarts after cooling both parts, then both parts are likely bad.

 

definately sounds like a bad coil or ICM. yes you can buy bad ones. Get quality parts. Dont cheap out

 

First: I tried the cold air trick, didn't help!
Put 2 new coils in it, the newest one is an AC Delco.
Had the new ICM tested fifteen time to get it nice and hot! Still good!

Second: I cleared the codes several times, and all I have to do to set them off again is crank the car over for about 10 seconds. Doesn't even have to start!

Today I checked the conector to the ICM with a continuity tester.
I got continuity from terminal B to the 9 pin in the PCM C3 conector. (good)
I got continuity from terminal C to ground. (good)

Here's where it gets tricky! Terminals A and D the pink wires, which have voltage running through them with the key on car not running. With key off and battery disconected, had continuity to ground (lit the test light)!!

Does this mean there's a short in those wires somewhere?
What's the best way to find the short?

 

First, let me make sure I understand the timing on the P1351 code. You clear the codes, then you crank the starter, the P1351 returns instantly and the engine starts and runs?

Or does the P1351 return instantly and the engine won't start?

What is your threshold for "continuity"? How low is the resistance (in ohms), for example, on the black wire to ground?

If it throws a P1351, and starts anyway, and your coil resistance is in spec (I'm thinking now yours should be 0.5 - 1.5 ohms) and your module is known to be good, then the PCM is bad.

The only other part I've ever seen kill spark in a "fails when hot" mode is the crank position sensor. That won't throw a P1351 code, though.

Oh, and the "2" after the S means yours was assembled in Moraine, Ohio.

And I just received several (5 sets of 2 to 4 pages each) ECM/engine wiring diagram pdf's for 1995 models from a source I refer to. I was only aware of one of these permutations, and I knew about the TBI versions in 1995, but I've never seen those in Blazers or Jimmies.

One of these diagrams looks like your system (two pink wires on the ICM plus data on pin 2 of the DLC to talk to the Innova scan tool). This is the first system I've seen with data on pin 2 of the DLC that wasn't OBD-II certified (it lacks other hardware required to support legally mandated OBD-II DTCs and PIDs).

 

Right now the engine won't start, just cranks over, but still throws the P1351 code after I reset it, and try to start the car.

Don't know the threshhold for continuity, I'm using a continuity test light.

The conector is 4 prong: A: pink B: white C: black (ground) D: pink

A. And D. have power to them with key on, that means they shouldn't have contnuity to Ground with key off and battery disconected. Is that correct???

Would a short at this piont cause the car to not start??

My Innova code reader is reading the J1850-VPM data, (Works on my car!)
My Cen-tech reader is reading J1850-PWM data, (Doesn't work on my car!)
Also the Cen-tech doesn't have all 16 pins in the conector! Came that way, Not sure why.