JohnCA58

How many wire CPS is that, 2 or 3 ?

Ahsai

3 wires. 2 for the coil and one for the cable shield.

TonyTwoBags

CPS issue is gone. Snuck in two canyon drives for the first time in a month or two.

JohnCA58

OK, thanks, so it is not a hall sensor.

Ahsai

Nope, it's just a simple coil (with a magnet next to it) for robustness, reliability, and simplicity.
The cam sensors are hall effect sensors.

JohnCA58

Thanks again, I was thrown for a bit because of the shielding on a A/C output sensor, on the diesel side we never had any shielding on that type sensor, only on data communication wiring and throttle position wiring, back in early 2000's the A/C output sensors were popular but failures were common, all speed/position sensors in use with today's engine are hall effect sensors with far fewer failures.

Di Zhao

OP, I am diagnosing the sensor as well. What is the voltage from the 3 wires when engine is not running? I know one is ground. When I measure the other two, both are giving me 2.5V....Do you happen to know?

mklein9

Oh my, it's been a long time. I looked over the thread and didn't see where the DC voltages of the CPS signal wires were ever measured (may have missed it though). Anyway, when the engine is not running, the two signal wires should be at some equal DC voltage since the CPS is a magnetic pickup and will only force a voltage when it's picking up movement, i.e. a changing magnetic field. It's probably likely that the DME biases the wires to some value convenient for detecting an AC signal, and I'd guess 2.5 V which is half the 5 V the DME runs on. So, both being 2.5 V sounds, at first glance, like the right condition.

BTW since fixing this issue and a similar throttle positioner issue (poor electrical contacts), the engine has accumulated about 45k miles and it has been running perfectly.

Di Zhao

Thank you for prompt reply. My problem is very intermittent, random misfire on both banks without another codes. Still don't know what condition causes the issue. So my guess is the cps. Check fuel pressure and it was good. Also replaced coils and plugs, but issue still exist. Vacuum is good too. Will be looking at scope this weekend and see if I have any luck. When there is no misfire, car runs strong.

Di Zhao

MK, according to wiring diagram, there is a ground shield, does it suppose to touch vehicle frame? I accessed the DME, connector III and found 980ohm to the crank sensor on pin 46 and 32, which indicate that the connectivity is good for the sensor coil. But the ground wire pin 45 is open and doesn't go to the vehicle ground. And when I measured the connector side under the car next to the sensor, the ground does connect to vehicle ground. Thus I think it means there is disconnect somewhere? I guess my other question is, does the DME pin 45 goes to vehicle ground or it should be insulated?

gidget11

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Di Zhao

Thanks for sending this tip. Sorry hadn't had a chance to report the final fix. After so much diagnostic, the issue revealed itself when I decided to rebuild the entire wire harness in the engine bay. It was the darn wire harness!. The wire was shielded and the shield was in bad shape. That explained why car misfired randomly only at lower rpm, as the voltage from the sensor is proportional to rpm. The ecu couldn't get a clean signal when rpm was low without a good shield. I had to route a new shielded wire (from local harware store) to bypassed the original harness from cps directly to the ecu. It worked perfectly and no misfire for 2+ years now.

dporto

Always nice to have a happy resolution!