dieseldave24v

Pulled the codes and here they are......

P0336 - Crank pos sensor A circut range
P1698 - No CDD message from TCM

Can I check the crank positioning sensor by resistance? Seems like I should be able to. I wouls assume it is just a transducer, but I have yet to pull it out

Dave Miller

I don't believe you can test it without a frequency meter or oscilloscope to read the output pulses. If unplugging it doesn't change anything then you probaly need to replace it. The voltage for it comes from the PCM, so you can verify connections at the PCM and at the CPS and verify the 5 volts at the PCM and at the CPS. You can try verifying the gap is .050 at the damper.

Cost about $75-100 to replace it. Napa got one for me.

dieseldave24v

Ok I am sold, going to napa, I will change it and eliminate this problem, I still dont see how this would cause the other guages to not work. Can anyone shed light on this

Dave Miller

I don't know what those codes mean. My 97 PCM manual does not list those codes. Maybe someone else can tell you the tests for those codes. I bought this PCM manual after all the problems I had a few months back trying to figure this all out and replacing the PCM ($600..ouch) and it was the $100 CPS that was bad.

Funny thing is my 97 PCM manual has no troubleshooting description for the CPS. I got the manual on ebay for $50 I believe.

If the CPS is shorted then the PCM doesn't work at all (what happened to me) and the key on gage light check will not light anything. I know I did not have the PCM supplied 5 volts at my CPS and I think the PCM was not functioning due to that short. When I unplugged the CPS I got the gage lights with key on back.

The CPS is critical to the PCM to determine that the engine is spinning. The PCM may be programmed to not display gage info if the CPS appears dead....I'm guessing here. If your tach works then the CPS is at least suppling some pulses to the PCM and the ALT should be charging.

I know its hard to figure these things out sometimes. Most of the time the PCM is good. The CPS is cheaper so I would try it first. I'm not saying thats it for sure.

Your 99 also has a ECM I believe and I don't know what it does...my 97 does not have an ECM.

Good luck,
Dave

dieseldave24v

Well just got back from the store, climbing under the truck with a sensor. I will let you know. Thanks for the help.

dieseldave24v

well still no luck now I have a P1698

dieseldave24v

Got it, The problem was the ground wire going to the PCM had a positive charge. I ran a ground to the computer and the alternator started charging. Cleared the codes and the have not come back. Thanks for the help guys.

dieseldave24v

Ok nevermind, Here is the deal The truck runs great with a new ground wire run to the PCM, until it melts the wire. How is this happeneing?

dieseldave24v

When I hook a ground wire from the PCM mounting bolt to the battery they wire sparks. This tells me the computer case is getting a positive charge from somthing.

Dave Miller

Put your voltmeter black gnd lead on the mounting bolt of PCM and voltmeter Red pos lead to battery 12v + post and see what you read. Sounds like you need to verify your grounds and power to PCM. If you think a gnd lead or mounting bolt is 12v prove it by putting the plus lead (red) of voltmeter to the gnd lead you think hot (or mounting bolt) and put the negative lead (blk) of voltmeter to chassis or neg of battery. If the gnd is hot you will read 12v.

You can verify a gnd lead on pcm is gnd but putting your voltmeter gnd lead on it and the positive (red) of voltmeter to 12v plus of battery. If its really gnd you will read 12v. You are using the voltmeter from 12v pos battery lead and looking for the gnd of the pin you think is gnd to have the voltmeter read 12v

I hope that makes sense.

sweeney186

Pcm grounds are pins 31 & 32 in the c1 black conn black/tan wires.There is also a large grey single conn by the pass batt-black/tan wire that can also cause pcm ground issues

dieseldave24v

The PCM will only ground and work properly if I ground it to the battery. If I ground it to a chassis ground or body ground nothing happens.

Dave Miller

Sounds like your ground strap to the engine from the batteries is loose or corroded. There should be no difference in grounding to frame or neg of battery if grounds are good. I'd be checking the ground to battery real close...use a jumper cable from neg of battery to the frame or body and retry gnd PCM from bolts. You could use an ohmeter from neg of battery to frame and read close to 0-1 ohm between them. Make sure first that there is no difference in voltage between the 2 points with the voltmeter first.

Check your 12v and grnds to pcm first. Clean your pcm grn mounting posts and be carefull or you may fry that pcm. I'm not familiar with the 99 PCM but someone should chime in here and tell you what pins to check for power and gnd.