'94 Strange error code behavior

[David1966]

My brother and I have been working on a 1994 LeSabre that used to belong to my uncle and has been sitting around relatively unused for about five years.

We've done all the normal things for putting a car back into service, which, for this car, included new spark plugs, new air filter, and a new oxygen sensor. We did get an error reading on the throttle position sensor, but removing its connector and cleaning the contacts with DeOxit fixed that problem and stopped it hesitating on acceleration from a stop.

Now, it runs perfectly, but we're still getting an error code of P0342, Low Cam Sensor Input Voltage. My brother thought it must be the sensor and replaced it, but we still get the error code. He can clear it using the Actron CP9145 code reader we bought, but it comes back again. The Service Engine Soon light is still on. And we checked the cam position magnet; it's right where it's supposed to be.

Our problem is that the inspection authorities around here probably won't pass the car with the Service Engine light on.

Any ideas about what could be generating this error code even though the car runs fine? Could it have a bad ECM? Could it be something to do with the crank sensor, since I read somewhere that they share a supply voltage? I wish I had an actual schematic of the computer/sensor system.

This has us stumped. Any suggestions will be appreciated.

Thanks,
David

[tman]

Pyll the bulb and get it inspected, then you have all the time in the world to figure out whats wrong.

Or, depending on how observant the mechanic is, use electrical tape to cover the light.

[Jed Rule]

The cam and crank sensors are powered by the Ignition Control Module. Try this:
Disconnect Cam position sensor connector.
Turn key on.
Using DVM measure voltage betwen harness connector pins A-B.
It should read 5-7 volts.
Measure voltage between harness connector pins B-C.
It should measure Battery voltage.

Give me your results and I can lead you further.
You could have a wiring /connector problem or a bad ICM

[David1966]

Hi Jed,

Thanks for the offer of help.

The voltage between pins A & B is 6.56 volts; the voltage between B & C is 11.38 volts.

Does this give you any clue as to what the problem is?

I haven't yet gotten my hands on a complete schematic of the system, which would be of great help, especially since I'm a fairly skilled electronics tech (in audio).

David

[Jed Rule]

Next step:
With key on and engine off measure voltage at PCM terminal RB9.
RB9 is in the red connector at the PCM. It is a solid black wire.
It should be 5 volts. If you don't get 5 volts, you might have to bump the engine with the starter if the Cam sensor happens to have stopped in a position interfacing with the magnet.
Start engine and read voltage after 1 minute. It should be varying around a mid-point of 4.6 volts.

I was just reading a post under LeSabre about a missing cam sensor magnet. That's possible but there are a few more tests. Post your answers and I'll take you further.
I am using a 95 GM Service manual and assume your car is the same.
They didn't go to OBD II till 1996.