Cam sensor

[HOTSIX]

Took another shot at my motor today....still no luck. I tried to re set the cam sensor as advised and as I did so...I was getting 6.XX voltage readings then all of a sudden it goes to zero without me turning the cam sensor.

I thought I heard something shorting out when voltage went to zero...like a wire when it grounds out...in and around the coil pack / module. Does the coilpack and module have to be grounded to the bracket ? If so...I just had it sitting on the bracket not bolted in just yet and their may not have been a good ground. Anyone have this happen before ?

First guess is I should check the fuses I suppose...and the "B" wire from the cam sensor may also have been the wire I heard short out when it was live. You guys think this is a fuse thing or worse....?

 

[cool 84]

Coilpack and module must be grounded for anything to work. You will get weird readings from the cam and crank sensors if it's not grounded and needless to say the car won't start.

 

[HOTSIX]

Cool...

Hey Cool84 when u say grounded you mean the module and coil pack bolted to the bracket or do you mean something else...?

I have all the harness wires connected...and I am sure one is a ground...but my question is does it need to be bolted securely to the metal bracket on the front of the engine ?

 

[KendallF]

Re: Cool...

Originally posted by HOTSIX
Hey Cool84 when u say grounded you mean the module and coil pack bolted to the bracket or do you mean something else...?

I have all the harness wires connected...and I am sure one is a ground...but my question is does it need to be bolted securely to the metal bracket on the front of the engine ?

The coil pack is case grounded; i.e., it gets its ground through the case to the bracket, and whatever the bracket's bolted to. If you've painted the bracket mounting surfaces or if it's loose, it will not have an adequate ground. My powdercoated intake required a separate ground run to a bolt on the bracket.

HTH,

 

[HOTSIX]

There's more....

I checked the cam sens again today...heres the update.

Voltage comming out of the module to the cam sens connector and wires is 7.XX
When I connect the cam sensor...the voltage immediately goes to 0.85 - 0.78 or so. Even if I turn the sensor - no change. It is mating with the helical gear insid the block properly too....all my wire connections have been checked and are good.

When I set the cam sensor before the voltage showed 7.XX after it was plugged in. Then I turned it counter clockwise to set it properly. It still refused to start. Worked before...but not now.

Do I have a bad cam sensor ??? Have I shorted out something to fry the sensor ??
Wires on the cap of the sensor look good...not loose...

How do you tell if you have a bad cam sensor ?

 

[KendallF]

Re: There's more....

Originally posted by HOTSIX
I checked the cam sens again today...heres the update.

Voltage comming out of the module to the cam sens connector and wires is 7.XX
When I connect the cam sensor...the voltage immediately goes to 0.85 - 0.78 or so. Even if I turn the sensor - no change. It is mating with the helical gear insid the block properly too....all my wire connections have been checked and are good.

When I set the cam sensor before the voltage showed 7.XX after it was plugged in. Then I turned it counter clockwise to set it properly. It still refused to start. Worked before...but not now.

Do I have a bad cam sensor ??? Have I shorted out something to fry the sensor ??
Wires on the cap of the sensor look good...not loose...

How do you tell if you have a bad cam sensor ?

To check the sensor, plug it in and spin it by hand while it's out of the motor. You should see the voltage on the middle pin (the signal out) drop from ~7.9 volts to somewhere ~1 volt somewhere during a full revolution. You may not be turning it far enough in the motor. Pull the cap and inspect the pickup to make sure the wires look OK there and the rotor is not messed up.

If the signal fails to transition during a full revolution, odds are decent that it is defective or you have a problem in the wiring from the module. If you can apply 12v and gnd to the sensor with it unplugged from the harness of the car, you can spin it and check for signal to eliminate harness problems. Casper's tester works great for this.

Good luck,

 

[cool 84]

I've had the same problem as you. I ended up having a bad cam sensor one time. Another time I had the cam sensor plugged in to where the injectors are supposed to go. Another time I had a broken ground wire where are the grounds are below the AC compressor. The bracket itself needs to be grounded. I use an extra ground strap bolted to the bottom of the module just to be safe.

 

[HOTSIX]

Well....it seems GM wants a real stack o cash for a new one...
and i'm sure that my problem.

Full reveloutions...no change in voltage. The module seems to have a decent ground as well 'cause the plugin for the sensor has decent power to it...like 7.XX v on the "B" wire and 10.XX on the grey/red wire. Pickup in the sensor must be fried...I dropped the bare wire I had stuffed into the plugin connection (when it was hot) and I think it hit the block the other day...may have fried the pickup I guess....

Anyone got a cam sensor to sell me ? or any suggestions where to get one ???

 

[HOTSIX]

UPDATE ON CAM SENSOR

Get this....

To confuse matters even more.....when I pull the sensor outta the motor to check it...hook it up and power it - I got the same results.

UNTIL I moved the module / coil off the bracket ! Then I got 8.XX v on the sensor. As soon as I ground the sensor on its bracket....I get 0.89 v reading on "B" wire.

(The 8.XX v wouldnt disappear when I spun the top of the sensor though...so I still might have a bad cam sensor....)

Whats with this strange voltage reading......Bad module ?