98 GTP: P0341, p0171, p0302

The dreaded P0171 has returned with a rough idle and high fuel trims at idle; fuel trims decrease when driving. P0341 and P0302 are also showing on the list of codes. I'm tackling the P0341 hoping that fixing it may fix the other codes, too.

P0341 indicates a camshaft position sensor fault. I've followed the diagnostic procedure in the FSM but am unsure about some results. To check the sensor, the procedure is to place a magnet next to the sensor and monitor the voltage at the PCM input. With no external test magnet, the voltage is +5VDC. When placing one side of the test magnet against the sensor, there is no change in voltage; but when I flip the magnet over, the voltage goes to 0VDC. The sensor may be sensitive to the magnetic pole but that's not indicated in the FSM. So I'm unclear if this indicates a bad sensor or not.

One of the subsequent procedures is to re-install the CMP sensor, jog the starter, and monitor the sensor voltage toggling 0 - 4 VDC. I saw fluctuations of 5 - 5.2VDC or so, but I have a digital multimeter. I wonder if the DMM is sensitive enough to measure the fluctuating voltage properly.

If the expected fluctuating voltage is absent, the FSM says to replace "the camshaft position sensor magnet. Refer to Camshaft Position Sensor Replacement." Is this referring to the magnet on the sensor and therefore replacing the sensor? Or is this referring to a magnet on he camshaft that is to be sensed? The replacement procedure doesn't mention such a magnet.

Any guidance is appreciated,

If this is a Buick 231 V6, the magnet for the CMP may be bonded into the cam sprocket.

http://padgett.performanceresearch.us/cars/cammag.htm

I don't know if this will help, but on my 97 Riv I was chasing my tail with the same issue after a ton of head scratching much searching on the web I came across a post that suggested checking wiring, the wire is a black one, it's on the lower left corner of the harness block on the firewall, behind the transmission dipstick,to the left of the booster and to the right of the cruise unit, it's a little tight to get to, but as I recall there's cover that has a screw holding it on, with it off it's easy to get to the wire, my looked fine and when I went to touch it, it broke kinda close to the pin, but I was able splice in some wire, and that fixed it. Might be worth checking.

I don't know if this will help, but on my 97 Riv I was chasing my tail with the same issue after a ton of head scratching much searching on the web I came across a post that suggested checking wiring, the wire is a black one, it's on the lower left corner of the harness block on the firewall, behind the transmission dipstick,to the left of the booster and to the right of the cruise unit, it's a little tight to get to, but as I recall there's cover that has a screw holding it on, with it off it's easy to get to the wire, my looked fine and when I went to touch it, it broke kinda close to the pin, but I was able splice in some wire, and that fixed it. Might be worth checking.

The CMP sensor wiring goes to the ICM on this car and the ICM goes to the PCM through the main wiring harness. Because I got steady voltage at the PCM harness, I think the wiring is ok. But always good to be suspicious of wiring in these old cars!

Replaced CMP sensor which apparently fixed P0341. Replaced oxygen sensor because that was next on suspect list for P0171, but no improvement. A little judicious use of carb cleaner showed leaks at the fuel injector O-rings...AGAIN. I just replaced those about a year ago! Well I replaced them again and spent considerable time trying to ensure they are seated correctly. So far, no codes.

But, the next domino has fallen. Took the car for alignment and state inspection. The shop proceeded to tell me that the car needs $3000 work just to pass inspection! They say there is play in the wheel bearings and inner tie rod ends, and they won't pass inspection. They pointed out power steering fluid leaks in the rack, high pressure line, and pump. Oil pan leaks. Transmission pan leaks. Flush and fill all the fluids. Seemed like they were piling on what they could. My dad recommended these guys for alignment so I bought a five year plan from them last year. And having them inspect was convenient. Won't do that again.

Now to figure out wheel hubs and inner tie rod ends, and later steering rack leaks.

That doesn't sound like $3000 in repairs. The rack can be replaced for ~$200 or less. That will take care of some of the leaks as well as the inner tie rods. The front hubs can be replaced for ~$220 with good quality Moogs. You'll have $100 into a trans pan drop and fill to replace the gasket and filter. Oil leaks can usually be fixed for next to nothing.

If you do the repairs yourself you'll have a day or two into it and have less than $600 in repairs. If the car is really that bad then it may just be time to let the car go.