Camshaft Position Sensor Circuit

[emtbjb]

I have a 1998 V70-XC that will not start. I have checked the crankshaft sensor, the camshaft sensor and the coil by the book. All the sensors test out ok, but when I tested the camshaft position sensor circuit, plug 1 test with good ground, wire 3 was battery voltage, but wire 2 was also battery voltage. According to the testing procedure, wire 2 was supposed to have 0-5 volts. I check the wires and there was no short. What I want to know, is the ECU shorted out or is there something else? Also, I replaced the ignition switch with a new one. Does anyone have any experience with this?

[Ozark Lee]

Welcome to MVS,

How are you testing this? Is the sensor plugged in or are you just plugging your meter into the connector that goes to the sensor with the sensor unplugged?

The proper procedure is to backprobe the connector with the sensor plugged in. If that is indeed what you are doing the sensor is bad and it will prevent the car from starting.

...Lee

[850tech]

Just took a quick look on alldata and those values are correct, with the sensor disconnected B+ (12v) on 2 and 3, and ground on 1 edit: on the engine harness side obviously

Any Codes? If so post them and me or someone else here wil let you know where to look as soon as possible. Also have you checked all your basics?
Fuel, spark and injector pulse? we need to know so you can narrow it down. For example if you have fuel, but no spark or injector pulse them a crank or cam sensor could be the issue, but you don't want to get into the complicated when something as simple is as the fuel pump relay (most common) could cause the same no start issue. Let us know if it's fuel or spark your missing, and don't worry about injector pulse, I understand most don't have that kind of test equipment.
I'm sure we will be able to help you figure it out.

[emtbjb]

I am testing the camshaft position sensor with a meter plugged into the connector that goes to the ECU. This is according to the test procedure by Chilton, Hayes, and Volvo. It calls for testing the values at the harness on the engine side unplugged from the sensor. I do not have an account with Alldata. I have pulled a P0340 code. I have good fuel pressure, no spark, and have not checked the injector pulse yet. When I do backprobe the camshaft sensor and crank it, 3 has battery volt, 2 goes between battery volt and 6.5 volts.

[850tech]

I'm really sorry it's taken me so long to reply, with all the heat lately lots of cars have been breaking down and I've been working extra hours.

Here's the diagnostic procedure for P0340, which is a cam sensor fault, as I'm sure you know. Don't bother checking for pulse as with P0340 you won't have it. Go through this step by step and you should find your fault. The voltage change on pin 2 would suggest the cam sensor magnet is picking up the cam rotation, but that does not mean the signal is clean or it's frequency is correct, so if all the wiring checks out I would go ahead and replace the sensor.


Checking Ground Lead

Ignition off.
Wait for approx. 150 seconds (cars with immobilizer 245 seconds).
Disconnect the camshaft position (CMP) sensor.
Connect an ohmmeter between the camshaft position sensor connector 1 (engine control module (ECM) side) and ground.
The ohmmeter should read approx. 0 ohms .
If reading is OK:

Proceed to Checking Power Cable section below.
If reading is incorrect:

Proceed to test step below.

Checking The Engine Control Module Connector

Ignition off.
Camshaft position sensor disconnected.
Check engine control module connector for contact resistance and oxidation.
Engine control module connected.
Connect an ohmmeter between the camshaft position sensor connector 1 (engine control module side) and ground.
The ohmmeter should read approx. 0 ohms .
If reading is OK:

The diagnostic trouble code (DTC) was caused by poor contact in the engine control module connector.
Then proceed to Verification section below.
If reading is incorrect:

Check cable between camshaft position sensor terminal 1 and engine control module # A18 for an open-circuit.
Then proceed to Verification section below.

Checking Power Cable

Ignition on.
Camshaft position sensor disconnected.
Connect a voltmeter between the camshaft position sensor connector 3 (engine control module side) and ground.
The voltmeter should read battery voltage .
If reading is OK:

Proceed to Checking Signal Cable section below.
If reading is incorrect:

Proceed to test step below.

Checking The Engine Control Module Connector

Ignition off.
Camshaft position sensor disconnected.
Check engine control module connector for contact resistance and oxidation.
Engine control module connected.
Ignition on.
Connect a voltmeter between the camshaft position sensor connector 3 (engine control module side) and ground.
The voltmeter should read battery voltage .
If reading is OK:

The diagnostic trouble code was caused by poor contact in the engine control module connector.
Then proceed to Verification section below.
If reading is incorrect:

Check cable between camshaft position sensor terminal 3 and engine control module # A36 for an open-circuit.
Then proceed to Verification section below.

Checking Signal Cable

Ignition on.
Camshaft position sensor disconnected.
Connect a voltmeter between the camshaft position sensor connector 2 (engine control module side) and ground.
The voltmeter should read battery voltage .
If reading is OK:

Proceed to test step below.
If reading is incorrect:

Proceed to Checking Signal Cable Resistance to Ground section below.

Checking The Signal Cable Voltage

Ignition on.
Camshaft position sensor disconnected.
Connect a test light between camshaft position connector terminal 2 (engine control module side) and ground.
Does the test light light up ?
Yes:

Check cable between the camshaft position sensor terminal 2 and engine control module # A21 for a short-circuit to supply voltage.
Then proceed to Verification section below.
No:

Proceed to Check Of The Camshaft Position Sensor section below.

Checking Signal Cable Resistance to Ground

Ignition off.
Wait for approx. 150 seconds (cars with immobilizer 245 seconds).
Camshaft position sensor disconnected.
Connect an ohmmeter between the camshaft position sensor connector 2 (engine control module side) and ground.
Is resistance Infinite ?
Yes:

Proceed to test step below.
No:

Check cable between the camshaft position sensor terminal 2 and engine control module # A21 for a short-circuit to ground.
Then proceed to Verification section below.

Checking The Engine Control Module Connector

Ignition off.
Camshaft position sensor disconnected.
Check engine control module connector for contact resistance and oxidation.
Engine control module connected.
Connect an ohmmeter between the camshaft position sensor connector 2 (engine control module side) and ground.
The ohmmeter should read 0.5 - 3.0 k ohms .
If reading is OK:

The diagnostic trouble code was caused by poor contact in the engine control module connector.
Then proceed to Verification section below.
If reading is incorrect:

Check cable between the camshaft position sensor terminal 2 and engine control module # A21 for an open-circuit.
Then proceed to Verification section below.

Check Of The Camshaft Position Sensor

Connect the camshaft position sensor.
Try to start the engine.
Does the engine start ?
Yes:

The cause of the diagnostic trouble code is poor contact in the camshaft position sensor connector and/or the engine control module connector. Check connectors for contact resistance and oxidation.
Then proceed to Verification section below.
No:

Try a new camshaft position sensor.
Then proceed to Verification section below.

Checking Camshaft Position Sensor Signal

The camshaft position sensor can malfunction due to a short-circuit to supply voltage in the signal cable. Check camshaft position sensor as follows.
Connect the camshaft position sensor.
Try to start the engine.
Does the engine start ?
Yes:

Camshaft position sensor OK.
No:

Try a new camshaft position sensor.
Then proceed to Verification section below.

Verification

After carrying out the repair, check that the fault has been remedied as follows.
Ignition off.
Reconnect connectors, reinstall components.
Try to start the engine.
Does the engine start ?
Yes:

Fault corrected
No:

Proceed to test step below.
Fault-tracing Information
The verification result shows that the fault persists.

Do you want to exit fault-tracing?
Yes:

Fault not corrected
No:

Return to Checking Ground Lead section above.

[emtbjb]

I worked. She lives again. Thank you so much for the help. It's nice to have received the correct information. Chilton has the wrong voltage for wire #2. You've saved me lot of $ and time.

[850tech]

Your welcome, and thank you for posting a follow up so people searching for information on this code in the future know this thread lead to a successful diagnosis. There is nothing worse then reading a page or two of post that look promising, only to have the topic suddenly end with no resolution, leaving you wondering if any of the solutions worked, and more importantly if any are worth spending time and money on.

[lhailah]

850tech, great steps, thanks a lot for sharing that. I have the same code reading and try to diagnos this way. however i'm stuck at the Check cable between camshaft position sensor terminal 3 and engine control module # A36 for an open-circuit.
I know where the ecu is but how do I find to connect to #A36. I've never got into the computer compartment before and dont know what to expect under those silver boxes.

Is this step to tell me if there is a problem with the computer or the wires. wouldn't i get other trouble codes if there were a problem with the computer?

[BEJinFbk]

850tech - Great writeup! Nice list. Someone should get this into the database.

FWIW, I came out to my car a few days ago and after only 5 minutes, it wouldn' start. It just spun.
I always carry my reader ( Isn't that what the pockets on the seatbacks are for? ) and got P0340.
I opened the hood, unplugged the CPS and plugged it back in. Voila! That's all the attention it wanted.
Reseating the connector is always worth a shot...

[lhailah]

i wish it were that simple for me.
installed new cam and crank sensor and still no spark. Had my two mechanic buddies check it out and nothing.
CAn anyone shed some light?