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Volco ec240 cam position sensor

BigWrench55

BigWrench55

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FWF,
Correct me if I'm wrong,but I seem to remember that there are two types of speed sensors for that engine. I'm about to fire up the laptop to confirm that. Since you have so much more intimate knowledge with Volvo than I. I thought you would know the answer.
 
funwithfuel

funwithfuel

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Yes. 2 wire and 3 wire. That's what threw me when he kept mentioning a 3rd wire. I thought we would be dealing with the 2 wire since your schematic (which is correct for B series tier 3) showed only 2 wires. That was the head scratcher.
 
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kevman6

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I will test it in the morning, and also test the original one. I'm not sure the original one was bad. There is a short somewhere in the electrical system, because the backup alarm will chirp weakly even with the key off.
we unplugged it to keep the batteries from draining. I have no Idea where to start tracking that, but could it effect the cam signal?
 
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kevman6

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I also never found a code description for SE2703-08 which is what I get if I start the engine and while it's running I plug the cam sensor in. It will continue to run but trips that code
 
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kevman6

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I checked the old cam sensor off the vehicle, and ohms read 3.6K ohms. I checked the currently installed cam sensor in the engine and it measured 3.9K ohms.
 
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kevman6

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The error sheet you sent makes reference to possible incorrect distance from the sensor gear. How would this be measured? It's almost impossible to even get to the hole the sensor goes into. It seems this is the direction I have to go next
 
funwithfuel

funwithfuel

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Ones perfect. The other is close.
Post 24, you stated that you had .2 volts going to cam sensor. You shouldn't have any. Please find source of unwanted voltage. That's most likely causing your corrupt cam signal
 
funwithfuel

funwithfuel

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kevman6

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Doesn't the sensor need some voltage to return a signal to the ECM? I will be checking tomorrow also to find the bleed in voltage that allows the backup beeper to give a low pitched squawk with the key off. Somewhere I have a short traveling through. The backup alarm is on the other side of the engine, but if the short is close enough, maybe it could disrupt the signal
 
funwithfuel

funwithfuel

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Look for ground faults and failed diodes. On the bottom of the fuse panel. The short grey/black fuse looking things are quenching diodes. If they are in backwards or shorted, they can cause all kinds of whacky behavior. Also, take a sniff inside the fuse box. Be honest with yourself, does anything smell burnt? The earlier ones were prone to failure from water intrusion.
 
funwithfuel

funwithfuel

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kevman6 said:
Doesn't the sensor need some voltage to return a signal to the ECM? I will be checking tomorrow also to find the bleed in voltage that allows the backup beeper to give a low pitched squawk with the key off. Somewhere I have a short traveling through. The backup alarm is on the other side of the engine, but if the short is close enough, maybe it could disrupt the signal
Click to expand...
No, the sensor is generating its own square sine wave with the windows of the cam gear. Any voltage on the line, whether ac or dc will corrupt the pure signal generated by the sensor.
 
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kevman6

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Rechecked for voltage to cam sensor. I separated all the wires in the engine harness where thry plug into the ECU harness to separate the Cam and Crank shielded wires. I only measured .003V at the square end of harness near engine, on the EA 45-EA46 wires when harness was plugged into ECU with key off and Battery switch on.
How would I check if the quenching diodes are shorted? Are they marked directional?
 
funwithfuel

funwithfuel

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Yes, they're marked. There's an image on the bottom of the fuse box cover, match it up with the image on the diodes. .003v is negligible, .2v is not. Have you tried checking for errors since splitting the wires apart?
 
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kevman6

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I did attempt to start the engine with both sensors plugged in, and no start. Again starts with only Crank sensor plugged in. Same error code when ignition is turned on. SE2703-03.
 
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kevman6

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There is a wire that has been added to the fuse box which goes from the hot wire terminal on right side of fuse box to the
Ignition switch in the cab. The ignition fuse was still in it's proper position and not blown. I removed that fuse and engine still starts and runs. There must have been a short in this circuit at one time. Removal of the fuse didn't change the error code
 
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