Crank Position Sensor?

99 GTP 125K miles getting the P1361 and P1362 DTC's (yeah the infamous DTCs), usually accompanied with a slight hesitation / jerk / fishbite (however it might be described) around 40-45 mph typically. Symptoms also noticed while at a idle during a stop light, but usually noticed the tachometer almost dropping to zero (as if it was going to stall) but never does because the car surges to correct itself.

I already have ohmed out the wire between the pcm and icm for 3x reference signal. I verified that the both connectors are firmly attached and checked for corrosion and proper mating. I already have a new IAC and the TPS is fairly new . . . also checked the ground (all grounds for that matter) on the icm and it is good. As I am looking at the schematics in the helms manuals I am narrowing it down to in between the CKPS and the ICM.

The CKPS has failed on me before, causing a complete stall while driving, but I have't replicated a complete stall yet. The car starts normal every time. I know some would suggest the ignition switch for electrical abnomalities (the switch was replaced 50K miles ago) so I was wanting the opinion of the experts. CKPS seem like the right direction for T/S?

P1361 and P1362? Thats not good.

Since you have the Helm GM Factory Service Manual did you follow the troubleshooting routine specifically for these DTCs which are IC and Bypass mode issues related to the ignition timing and advance. Check the other wiring and signals such as the IC Timing Control and IC Timing Signal between the ICM and PCM modules. Ohm out point to point per the wiring diagrams and look for an open or short to ground.

The ICM module and PCM modules are possibilities after checking the wiring but will require controlled substitution to rule them out. Crank sensor is possible but based on the ability to start the car and it running without stalling probably not likely but you never know for sure.

P1361 Ignition Control (IC) Circuit Low Voltage (GM)
P1362 Ignition Bypass Circuit Low Voltage (GM)

When the tach drops toward zero, does the trac off light come on also? If so, I would suspect a CKPS could be part of the problem. If not, it may be an internally shorting ICM or a broken/partially broken wire somewhere up the harness either sending a weak signal or grounding out. The P1361 is set when the EST circuit fails to toggle on after the PCM commands it to.

T/S flow chart in the Helms manual pointed towards PCM. So I replaced the PCM with a zzp flashed version 1.0, while waiting for it I checked the wiring from underhood fuse box and back to pcm connector. I even checked the wiring from the ICM back to the PCM which all checked out fine.

Put everything back together started the car right up, let it sit running for approximately 15 mins. Turned it off, came back 5 minutes later to take it for a test drive around the block, no sooner getting out of the driveway and the car struggles like it was choking to keep running and then stalls. I didn't get the TCS off light until about a minute after it stalled. The only immediate indications of the stall was the oil and battery lights coming on and obviously the tach dropping to zero as the car died.

Upon attempting to restart it - was very intermittent, it would start and then die within seconds and another time start and stay running for a couple of minutes. I was able to get it running long enough to go in reverse before it had another hard stall (struggled not to stall - car was vibrating . . .). I even unplugged the MAF to see if the car would stay running and it didn't, it stalled just like any other attempt before.

Last time I had these symptoms it was very similar to the CKPS being bad, although not nearly as rough. Note: I didn't check the wiring from the CKPS to the ICM. A few questions, could these be symptoms from the car not having a CKPS learn? Would it be better to check the fuel pressure and fuel system first? Second note: Fuel pump and filter just replaced under 20K miles ago.

Note: I didn't check the wiring from the CKPS to the ICM. A few questions, could these be symptoms from the car not having a CKPS learn? Would it be better to check the fuel pressure and fuel system first? Second note: Fuel pump and filter just replaced under 20K miles ago.

Negative. The crank variation learn is only for the PCM module to discriminate between real or false misfires. It does not preclude the car from starting nor will it cause a stall condition.

Fuel pressure should always be checked to rule out a possible fuel supply problem.

Also, do you still have the original fuel pump resistor?

I actually still have the original fuel pump resistor and its probably a good consideration since while I was checking the wiring I was moving alot of wiring that I have routed behind the battery in that area. I believe that is relatively the same area where the fuel pump resistor is located?

Based on your varying symptoms it would not hurt and to rule out other possibilities with the least cost. You can remove the passenger side headlamp assembly to inspect the resistor. Plus you can try the bypass procedure at the link below. Easy and free. Also, swap out the fuel pump relay with the fuel pump speed control relay if that doesn't work.

Click here (http://www.automotiveforums.com/vbulletin/showthread.php?t=658282)

The fact that it is intermittent suggests something in the harness that's intermittently grounding out...or a component that's doing the same intermittently.

One thought is to "jiggle" the harness with the engine runnning, but I know where that harness goes (tight to the front cover/block/front head/coil pack bracket inside the belt drive) and so I can't recommend that...maybe poke at it with a stick or something safer than using hands directly. You could also do all the manual-suggested probe-checks with the engine off and have a helper wiggle the harness to make sure it is sound.

Regarding componentry think I'd try the ICM now, if it were me...as BNaylor states it will be controlled substitution and miles will have to build (or not) to determine whether that is the root cause.

The fact that the engine will sometimes "stall save" says to me it's getting the crank pulses...if not the tach drop would be a guaranteed stall in my thinking.

could be a loose connection on the PCM or damaged terminals(pins)
if other lights are on,

Sorry for taking so long to get back on this issue. I went ahead and tried the fuel resistor bypass procedure, the car still stalled. It was at this point I decided to replace the CKPS. While replacing I inspected and even replaced the wire harness after point to point ohming out each wire. Although I found nothing wrong with the wire the retaining clip had been broken for some time that's why I decided to replace with a pigtail. In fact, upon putting everything back together - replacing the CKPS didn't solve the issue.

I got frustrated and decided to buy an ICM, its not here yet, but in the meantime I was thinking of doing the plugs and wires. To double check when I last replaced them I pulled out my vehicle's maintenance history records (yeah I keep everything)! Found my receipts for when I recently replaced fuel filter, pump and one fuel relay, ICM (wish I would have looked sooner:banghead:), plugs and wires almost exactly 21K miles ago. Back then I didn't do the work myself, it was always cold in Montana with no garage! But the shop put in AP606 plugs and I'm assuming the equivalent of oem wires (p/n: 700984).

Today I went out and decided to switch the fuel pump relay and speed control relay, which didn't solve anything either. While I was outside decided its better late than never to check the fuel pressure which I found was at highest to be 44 psi, normally 42 after multiple readings. Also noticed if I let the gauge sit the pressure would leak quite fast. The pressure dropped to about 38psi within two minutes.

Before all this trouble I had recently done a zzp stage 3 IC install, and went with the $130 cheap zzp fuel rails. But now that I'm so far down this road of troubleshooting - I'm wondering which direction to take next? Check the fuel rails/system or is plugs and wires more of an obvious choice? Sorry that this post is quite long, I don't even know if this post should be a new one now that the issue seems to have changed? Thanks ahead of time for any input!

Went a bought a fuel pump resistor and relocated it to the engine bay today. Didn't change the fuel pressure any or help the stalling issue. Since my new ICM came in, I figured I'd give it a try. Upon installing it the car wouldn't start through two tries. Third times a charm and it started. While idling the engine had a few struggles bt saved itself by increasing the rpms for a few seconds, ran otherwise smooth for 14 minutes. Right when I was getting ready to shut it off - it struggled and then stalled.

Same scenario as with a bad CKPS but without a SES light. Tried a few times to restart it and wouldn't turn over. I hooked up the ODBII reader just in case I might get something and I pulled a P0340 Camshaft Position Sensor Performance. Haven't started to use the t/s guide in helms yet because I had a few questions first.

I'm wondering if the stalling issue and the cam sensor DTC are more related to the plugs and wires? Or even possibly the fuel pressure regulator?

Since you continue to have strange codes popping up, I still suspect the wiring either to the PCM, or between it and the ICM. Another thing you could try is unplugging the MAF sensor and see if it quits trying to stall. I've never seen a bad MAF trip the codes you have, but it will cause your hesitation/surging issue. Again, it's an easy free test that may narrow it down.

Unlike a lot of poor blokes we get at least you have a GM FSM so use the diagnostic and troubleshooting guides and see where it takes you.

On the P0340 DTC I doubt the wires or plugs will cause that. Did you ever get the other DTCs resolved? Mainly the IC and Bypass mode codes.

And what is the fuel pressure reading(s) now? At fuel pump prime and at idle. Also, with vacuum line at fuel pressure regulator on and off. Is it in specs? On a L67 GTP 48-55 psi.