Testing Crank Position Sensor?

Poncate · 06-01-2009, 12:01 AM

My check engine light is on and I did some searching on the forums and came up with the CPS. I checked the gap and it is on. I checked the power to the CPS and it is at 8v, then I checked the resistance across it and it reads an ~ of 18ohms.
Not sure what this reading means. I thing the sensor is bad but what do you all think?
Thanks in advance.

__________________
Stock 92, 4x4, IC, turbo, 5 speed, 4" lift.

Philip · 06-01-2009, 12:12 PM

I did a little playing around with a couple of CPS I have. From what I can tell the sensor is open when it sees metal. It closes when it hits the air gap in the balencer.

I know one of the sensors I have is bad. The other one is a question mark. The two I have did not transfer a full 8 volts back to the PCM. One only sent a 1 volt signal. The other was only around .05 volts. That is the known bad one. I made a jumper setup to test the one on my truck. I didn't have time to see what it is putting out.

__________________
93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto(G56 soon), 3:07's axles, 2" skyjacker lift, B&W flatbed

Poncate · 06-01-2009, 09:44 PM

Hey, thanks a lot Philip. Looking forward to hearing what a good one is supposed to read. Also, could you specify how you tested so I can make sure I am even doing it right.
thanks again

__________________
Stock 92, 4x4, IC, turbo, 5 speed, 4" lift.

Philip · 06-02-2009, 12:01 AM

Well I cheated. I have a regulated DC power supply. I just set the voltage for 8 volts and rigged the power to the correct pins. Then I just used a wrench to simulate the metal in the balencer.

I used the plug off the bad CPS. I took the female plug off the trash harness on my spare engine. I soldered them together and made a test jumper to use on my truck. That is after the moonsoon season goes away.

__________________
93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto(G56 soon), 3:07's axles, 2" skyjacker lift, B&W flatbed

Philip · 06-02-2009, 12:05 PM

Ok here is the way to test your CPS.

Black/blue tracer is the sensor ground wire. It should OHM close to zero to the battery ground.

Tan/yellow tracer is the 8 volt power feed to the sensor. The voltage regulators on the PCM's are kind of loose. This voltage can vary around some.

Gray/black tracer is the signal wire. If the sensor is on a smooth section of the balencer there should be little if any voltage showing. When the sensor is on one of the air gaps it should show around 5 volts.

If you have a 12 volt adjustable power supply. A 14 gage blue wire terminal will slide down over the male pins on the CPS.

__________________
93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto(G56 soon), 3:07's axles, 2" skyjacker lift, B&W flatbed

06-01-2009, 12:01 AM	#1 (permalink)
Poncate Cummins Fan Join Date: Mar 2009 Location: PNW Posts: 95 Thanks: 0 Thanked 2 Times in 2 Posts Poncate's Truck Pics	Testing Crank Position Sensor? My check engine light is on and I did some searching on the forums and came up with the CPS. I checked the gap and it is on. I checked the power to the CPS and it is at 8v, then I checked the resistance across it and it reads an ~ of 18ohms. Not sure what this reading means. I thing the sensor is bad but what do you all think? Thanks in advance. __________________ Stock 92, 4x4, IC, turbo, 5 speed, 4" lift.

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06-01-2009, 12:12 PM	#2 (permalink)
Philip 1ST GEN MODERATOR Join Date: Nov 2007 Location: Indiana Posts: 6,268 Thanks: 5 Thanked 248 Times in 227 Posts Philip's Truck Pics	I did a little playing around with a couple of CPS I have. From what I can tell the sensor is open when it sees metal. It closes when it hits the air gap in the balencer. I know one of the sensors I have is bad. The other one is a question mark. The two I have did not transfer a full 8 volts back to the PCM. One only sent a 1 volt signal. The other was only around .05 volts. That is the known bad one. I made a jumper setup to test the one on my truck. I didn't have time to see what it is putting out. __________________ 93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto(G56 soon), 3:07's axles, 2" skyjacker lift, B&W flatbed

06-01-2009, 09:44 PM	#3 (permalink)
Poncate Cummins Fan Join Date: Mar 2009 Location: PNW Posts: 95 Thanks: 0 Thanked 2 Times in 2 Posts Poncate's Truck Pics	Hey, thanks a lot Philip. Looking forward to hearing what a good one is supposed to read. Also, could you specify how you tested so I can make sure I am even doing it right. thanks again __________________ Stock 92, 4x4, IC, turbo, 5 speed, 4" lift.

06-02-2009, 12:01 AM	#4 (permalink)
Philip 1ST GEN MODERATOR Join Date: Nov 2007 Location: Indiana Posts: 6,268 Thanks: 5 Thanked 248 Times in 227 Posts Philip's Truck Pics	Well I cheated. I have a regulated DC power supply. I just set the voltage for 8 volts and rigged the power to the correct pins. Then I just used a wrench to simulate the metal in the balencer. I used the plug off the bad CPS. I took the female plug off the trash harness on my spare engine. I soldered them together and made a test jumper to use on my truck. That is after the moonsoon season goes away. __________________ 93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto(G56 soon), 3:07's axles, 2" skyjacker lift, B&W flatbed

06-02-2009, 12:05 PM	#5 (permalink)
Philip 1ST GEN MODERATOR Join Date: Nov 2007 Location: Indiana Posts: 6,268 Thanks: 5 Thanked 248 Times in 227 Posts Philip's Truck Pics	Ok here is the way to test your CPS. Black/blue tracer is the sensor ground wire. It should OHM close to zero to the battery ground. Tan/yellow tracer is the 8 volt power feed to the sensor. The voltage regulators on the PCM's are kind of loose. This voltage can vary around some. Gray/black tracer is the signal wire. If the sensor is on a smooth section of the balencer there should be little if any voltage showing. When the sensor is on one of the air gaps it should show around 5 volts. If you have a 12 volt adjustable power supply. A 14 gage blue wire terminal will slide down over the male pins on the CPS. __________________ 93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto(G56 soon), 3:07's axles, 2" skyjacker lift, B&W flatbed