How to rewire a cam sensor?

[jayro]

Hello,
So I have narrowed down my bucking issue (214 CID code) to a wiring short in the Cam sensor wiring. I have replaced the cam sensor 3 times to eliminate the "Bad out of the Box" issue.

So the next time it started I went ahead and pulled the plug off the cam sensor. The issue cleared up. Drove around for a good 30 minutes and it ran fine. Am I correct in thinking that this has narrowed the issue down to a short in the Cam sensor wiring? If so, how would I rewire the circuit? A step by step with some diagrams would be awesome if its possible. Thanks

 

[pjtoledo]

more than likely you have an intermittant open circuit.

a "short " is when two wires are connected that shouldn't be. lots of current gets thru, wires get hot, fuses blow, breakers trip etc.
an "open" is when one of the wires breaks and no current gets thru.
they are common in aging wire harness's.
open the wire bundles and follow the wires, pulling at any junction or connector.

parts of that circuit are shielded. if the shield or its drain(ground) are bad, stray electrical interferance can cause false signals in the circuit.

Perry

 

[rubydist]

the cam sensor has 4 wires to it:

O/R circuit 259 is a dedicated ground for ignition related stuff including the crank sensor. it is unlikely you have a fault in this wire.

LB circuit 796 is a signal directly to the ignition control connector on the DIS. a fault here would raise all sorts of havoc.

G circuit 795 is a signal wire to the pcm. it goes from the cam sensor to the round 8-pin connector (that is populated with 5 pins) on the back of the engine and then to the pcm. a fault here would also be a problem.

R/LG circuit 16 is the power to the sensor. that power circuit also supplies power to the DIS and crank sensor. it is unlikely you have a fault on that circuit.

I would start by ohming out the resistance on circuits 796 and 795 (both including and not including the round 8-pin connector. be sure to wiggle the wiring as you are testing. most of these wiring faults are at connectors - where the pin meets the socket, and where the pin/socket are crimped to the wire are the most likely suspects.

 

[TimboSHO]

To add to what Perry said, if you had a short, you may still have the issue when the sensor is unplugged. You most likely have an open. The best way to find this is with a multi-meter set to reistance. Find both ends of the circuit and wiggle along the circuit to see if you can find the spot. The shielded circuits are more difficult to repair correctly, especially if the shielding is suspect. You would find bad shielding by testing the resistance between it and your suspect circuits.

Believe me, it's difficult to track down bad wiring in an SHO. I've spent over 20 hours each on two different cars (for no start conditions), and it's not very easy to follow some circuits, especially without taking a bunch of stuff apart, and taking the loom and electrical tape off.

So, I wish you good luck, but before you go re-wiring something, make sure you can verify the fault first!

 

[pjtoledo]

To add to what Perry said, if you had a short, you may still have the issue when the sensor is unplugged. You most likely have an open. The best way to find this is with a multi-meter set to reistance. Find both ends of the circuit and wiggle along the circuit to see if you can find the spot. The shielded circuits are more difficult to repair correctly, especially if the shielding is suspect. You would find bad shielding by testing the resistance between it and your suspect circuits.Believe me, it's difficult to track down bad wiring in an SHO. I've spent over 20 hours each on two different cars (for no start conditions), and it's not very easy to follow some circuits, especially without taking a bunch of stuff apart, and taking the loom and electrical tape off.

So, I wish you good luck, but before you go re-wiring something, make sure you can verify the fault first!

shields are grounded at one end, the other end is always unattached to prevent "eddy" currents. so a shield should be a dead short (or maybe 1 ohm) to ground. it would be open to any other circuit.


Perry

 

[pjtoledo]

the cam sensor has 4 wires to it:

O/R circuit 259 is a dedicated ground for ignition related stuff including the crank sensor. it is unlikely you have a fault in this wire.LB circuit 796 is a signal directly to the ignition control connector on the DIS. a fault here would raise all sorts of havoc.

G circuit 795 is a signal wire to the pcm. it goes from the cam sensor to the round 8-pin connector (that is populated with 5 pins) on the back of the engine and then to the pcm. a fault here would also be a problem.

R/LG circuit 16 is the power to the sensor. that power circuit also supplies power to the DIS and crank sensor. it is unlikely you have a fault on that circuit.

I would start by ohming out the resistance on circuits 796 and 795 (both including and not including the round 8-pin connector. be sure to wiggle the wiring as you are testing. most of these wiring faults are at connectors - where the pin meets the socket, and where the pin/socket are crimped to the wire are the most likely suspects.

the manual shows a junction in circuit 259, S131 where the grounds from the cam sensor, crank sensor, ICM, and PCM all tie together. give those wires a good pull. 259 is a circuit ground, it does not go directly to chassis ground. it may be tied inside one of the devices, but does not directly tie to main ground.
if you have access to an O'cilloscope that would show a degraded waveform.


Perry

 

[jayro]

Thanks guys....doesn't sound like a whole lot of fun.

Ends up it may not be the circuit. Car ran fine with the Cam Sensor unplugged for half an hour last night. Ran fine this morning on the way to work (about another 30 min). Stopped and grabbed breakfast. When I came back out now it has a constant misfire. This misfire seems a little different and may be a different issue....acts like a bad coil pack,wire or plug. Seems to only be firing on 5 cylinders.

Man, if its not one thing it is 20. Car has run flawlessly for the time that I have had it. Ran perfect at the track for the last 2 years. Just started this misfire issue on the last half of the last day at the track.

Makes me think it is something electrical component. Seems to run well until it heats up. Then it gets flakey.

 

[rubydist]

there are 3 coils, so if you have a bad coil you will get 4 cylinders firing, not 5. if you have 5, then its a wire, plug or some other issue.

however, since both the power and the ground to the cam sensor are also power and ground to the DIS, it may be you have narrowed down your wiring problem...

 

[jayro]

there are 3 coils, so if you have a bad coil you will get 4 cylinders firing, not 5. if you have 5, then its a wire, plug or some other issue.

however, since both the power and the ground to the cam sensor are also power and ground to the DIS, it may be you have narrowed down your wiring problem...

I see. Sounds like a good place to start. Funny thing is that I came out after work and drove it home (about 45 minutes) with no issues....other than the CEL from the cam sensor being unplugged.

Another observations....if I start it up with the cam sensor unplugged I have no tach (to be expected). If I start it up with the cam sensor plugged in and then unplug it I have a tach until the next time I turn the car off. Probably has nothing to do with the issue, just something I noticed.

 

[rubydist]

that is curious. every time I have done that the tach went away as soon as I unplugged the cam sensor...
maybe the issue is a bad ground

 

[jayro]

that is curious. every time I have done that the tach went away as soon as I unplugged the cam sensor...
maybe the issue is a bad ground

I had gone through and cleaned all the ground path connections for the DIS/Intake. I was going to run a couple of independent ground straps to make sure the components were grounded well. Any specific location to apply them? I want to make sure the DIS and Cam sensor circuit are grounded well.

 

[rubydist]

yes, but you need the ground wire in the bundle to be good too - I would ohm out those 4 wires to see what you find. that is where I would go next given the situation.