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Andy, Volvo Expert Technician
Category: Volvo
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Experience:  One of only a handful of ACTUAL Volvo dealership technicians on JA, ASE Master Certified with L1
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1996 960 Volvo. Engine shut down during driving and, at stop

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1996 960 Volvo. Engine shut down during driving and, at stop fails to restart. OBD trouble code indicates PO340 :Cam Position Sensor: Fault Description, A Bank 1 Ckt malfunction. Disconnected cam position sensor and checked voltage, PIN 3 12v : PIN 2 12VDC ????: Pin 1 checked continuity to ground OK. I think that PIN 2 voltage should be 5VDC and not 12VDC: If the reading is 12VDC and not 5VDC does that indicate a fault at ECM (Eng controL). Is there another way to confirm that the problem is at ECM. Big bucks $$$ to replace ECM.
Could the cam position sensor have failed because of the higher voltage, 12VDC instead of 5VDC.

I don't have the wiring diagram in front of me, but I doubt it would be much help. The sensors on the 850s (which are the same) go bad all the time. The fault tracing for them is to check the ground and check for battery voltage on pin 2. If those are present, the sensor gets replaced. I have never replaced an ECM for a CMP code but I've replaced dozens of CMPs so I would certainly start there.

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Customer: replied 7 years ago.
I agree that the failure is more likely to be the sensor and not the ECM. I still want to know what voltages should be read at CMP connector pins 2 and 3. I have two sources that differ. Chilton says pin 2 is 5v and Alldata says pin 2 is 12v. If the CMP requires the lower voltage, 5vdc then putting 12 vdc on pin 2 may destroy the new CMP that I'll be installing. If the Chilton manual is wrong then I may be home free with a new sensor.

Volvo doesn't give us a spec for that in the fault tracing of that code. If you'd like, I'll check the voltages on my car (95 850) tomorrow and let you know- they should both be the same.

Well this was interesting... I measured the voltages at the CMP on my 95 850 and found 5V on pin 2. I also have a 98 V70R, so I checked that as well, and got 12V. Both use the same sensor as your car. If you don't mind waiting until tomorrow, I will find a 960 at work and measure that just to be certain. Unfortunately, the wiring diagram doesn't give any indication of what the voltage should be and I don't want to guess and have you fry the new sensor, even though I'm pretty certain your ECM is fine.
Customer: replied 7 years ago.
Andy, thanks for your follow-up. Yes I would be interested in the information on the 960. I think I have already given permission for payment. If not I'll follow-up to make sure payment was released.
Ps. I sure wish I had a copy of the ECM schematic to see if the signal voltage is clamped. If the voltage is clamped at 5vdc then the input line from the CPM sensor could be either 5vdc or 12vdc.

Here is the wiring diagram. The CMP is 7/21. As you can see, there is no indication at the ECM pins 10 and 8 as to what the wires do. Payment has been released so I will follow up with you tomorrow when I measure an actual 960.


Customer: replied 7 years ago.
Andy, thanks again.
Unfortunately we did not have any 960s come in today. I did, however, find a fault tracing guide for the Motronic 4.4 fuel system which says at pin 8 of the ECM you should have 5V with the key on. That is the signal from the CMP which alternates between 5V and 0V. It also says pin 2 should have 5V with the sensor disconnected which doesn't make sense to me since that is the signal wire from the CMP to the ECM. I'm still curious as to why my two cars have different readings with the same sensor.

What you need to do now is disconnect the ECM and CMP and see if there is still voltage on that wire which would indicate it is shorted to power. I would also check voltage at pin 8 with everything connected with the key on.
Customer: replied 7 years ago.
I ordered a new cps and should have it installed late next week. Will check voltages and if still ambiguous I'll keep my fingers crossed when I power it on. Andy, I think you're losing money on this problem. Left you a tip yesterday, hope you got it. Thanks again
All money has been received and is much appreciated. I'm not sure if you mention that because you are unhappy I was not able to measure an actual 960 but if you are dissatisfied let me know. I hope its just the sensor even though Volvo's confusing and inconsistent fault tracing book says 5V should be on that wire. Thanks again for your patience and let me know how it goes or if you have any other questions.
Customer: replied 7 years ago.
Andy sorry I am late getting back to you. Not at all about being unhappy. Ambiguity is with Volvo not you or me. I think you you did an outstanding job on this problem
Okay, I just wanted to make sure. We still have not had any 960's come in (we're slow and it isn't often bring the older cars to a dealer) but I'm keeping my eye out. Let me know if you have any other questions.
I finally had a 960 come in today. It was a 97 but it should be the same. It showed 12v on the signal wire with the CMP disconnected and the key on. Did you replace the sensor yet? Any luck?