Crank Position Sensor

[katrinekid]

I have a 94-1500-6.5TD. I pulled a code 19 (crank position sensor) and replaced and cleared codes but I am still getting a code 19. Any ideas
Hope someone can help. Thank you in advance!!!

[More Power]

The CKP sensor is a 3-wire unit. The PCM sends it a regulated 5 VDC on the wire (gray), it is grounded through the PCM on another (black), and the third is the signal wire (yellow), which again, goes to the PCM.

The ground lead is shared by a variety of engine sensors, so if you're only getting a CKP sensor code, the PCM is seeing/providing a ground, but it may not be reaching the CKP.

Likewise, the boost pressure sensor shares the 5 VDC line with the CKP, so the PCM is likely outputting the 5 volts, but it may not be reaching the CKP.

Might need to need to break out the DVM... :)

Jim

[katrinekid]

I forgot to include all the codes, SORRY. All the codes are 19,36 & 85.

[Robyn]

The 85 is an undefined ratio error.
The 36 is a IP pulse width error.

Having a spread of totally unrelated codes tells me you have either a voltage problem or a ground issue.
Check the battery cables.
The 94 has the alternator feed going to the LH battery and then the power crosses the core support on the large xover cable to the RH battery.
The RH battery feeds the trucks main power bus bar as well as the starter.

The gound cables often get coroded in the crimp area where the eye bolts to the engine block.
The side terminal cables are notorious for corosion under the colored jackets.

Be very certain that you have 14.2 to 14.7 Volts at both batteries.

If the LH battery ground fails the whole system can get wierd.

Now the power feed for the truck comes off the RH cable. This is a much smaller cable that snakes down along the block then comes up the firewall and goes into the junction block (Small odd shaped plastic box by the AC evaporator) Be sure you have 14.2+ volts at the power stud there.

Also check the ground cables that come from the main firewall wiring harness and attach to the RH rear of the intake manifold.

There is also a braided copper colored ground that is hooked to the body and to the rear of the RH head.

No real rule as to where it needs to be but a ground needs to be connected to the firewall from the engine.

If you have goofy voltage or grounding issues the system can get real hinky.
Be sure your alternator is doing its job well too.

Output at the Alt has to be seeing good voltage as well as the proper amps
If the altrernator has some diode issues it can be showing a voltage charge but allowing the sytem to actually fall off slowly. Also if the alternator has diode issues this can cause wierd anomalies in the elctrical system that can cause the ECM to get unhappy and when that happens its anybodies guess as to what can happen.

GM did not use very large wire on a buttload of the systems in the engine bay and when things start to get some time and miles on the clock issues can and do arrise.

Sort of a rule of thumb is if you see a bunch of unrelated codes to go check battery and system grounds as well as system voltage.

I have seen some rigs that the ECM was extemely fussy about this stuff and others that did not seem to mind some anomalies.


Good luck and let us know.

Robyn