CMP Sensor always reads 1012 RPM on Tech 2
Thread Starter
Safety Car
Joined: Feb 1999
Posts: 4,977
Likes: 10
From: Reno NV
CMP Sensor always reads 1012 RPM on Tech 2
I have a 2005 C6 that dies after 50 minutes of running.
I just did a Snapshot and it shows the CMP RPM at 1012.
Any thoughts on how that is possible?
Obviously something is wrong but what?
I'm not going to just throw a new PCM at it. But hopefully someone here has some experience with this.
I have a few threads out there trolling for answers. But I think this one may get some attention.
I just did a Snapshot and it shows the CMP RPM at 1012.
Any thoughts on how that is possible?
Obviously something is wrong but what?
I'm not going to just throw a new PCM at it. But hopefully someone here has some experience with this.
I have a few threads out there trolling for answers. But I think this one may get some attention.
Safety Car
Joined: May 2011
Posts: 3,807
Likes: 508
From: Oshawa, Ontario
I have a 2005 C6 that dies after 50 minutes of running.
I just did a Snapshot and it shows the CMP RPM at 1012.
Any thoughts on how that is possible?
Obviously something is wrong but what?
I'm not going to just throw a new PCM at it. But hopefully someone here has some experience with this.
I have a few threads out there trolling for answers. But I think this one may get some attention.
I just did a Snapshot and it shows the CMP RPM at 1012.
Any thoughts on how that is possible?
Obviously something is wrong but what?
I'm not going to just throw a new PCM at it. But hopefully someone here has some experience with this.
I have a few threads out there trolling for answers. But I think this one may get some attention.
Thread Starter
Safety Car
Joined: Feb 1999
Posts: 4,977
Likes: 10
From: Reno NV
I checked my truck, and the CMP changes RPM.
Each time I try it, the RPM number is different but static, but even with the engine not running it shows somewhere between (975-1060) and stays there until the next time I hook up the Tech 2.
Burning Brakes
Joined: Dec 1999
Posts: 765
Likes: 11
Cruise-In I Veteran
No, The CKP reads the actual RPM and dynamically changes
I checked my truck, and the CMP changes RPM.
Each time I try it, the RPM number is different but static, but even with the engine not running it shows somewhere between (975-1060) and stays there until the next time I hook up the Tech 2.
I checked my truck, and the CMP changes RPM.
Each time I try it, the RPM number is different but static, but even with the engine not running it shows somewhere between (975-1060) and stays there until the next time I hook up the Tech 2.
Pull the sensor and check the end to see if anything like metal bits is stuck to the magnet. The trigger is cast into the cam gear, so if the engine is running, that isn't your problem....
If you had a lab scope, you could watch the pattern to see if you are getting a good square wave pattern to figure out if its a bad sensor or if its further down stream, like the PCM.
Weird.... could be wiring, could be connector pins at the sensor and/or the PCM....
Good luck and keep us posted.
Thread Starter
Safety Car
Joined: Feb 1999
Posts: 4,977
Likes: 10
From: Reno NV
When you unplug the cam sensor and crank the motor, what does the scanner read? Is it "0?" or does it show a value?
Pull the sensor and check the end to see if anything like metal bits is stuck to the magnet. The trigger is cast into the cam gear, so if the engine is running, that isn't your problem....
If you had a lab scope, you could watch the pattern to see if you are getting a good square wave pattern to figure out if its a bad sensor or if its further down stream, like the PCM.
Weird.... could be wiring, could be connector pins at the sensor and/or the PCM....
Good luck and keep us posted.
Pull the sensor and check the end to see if anything like metal bits is stuck to the magnet. The trigger is cast into the cam gear, so if the engine is running, that isn't your problem....
If you had a lab scope, you could watch the pattern to see if you are getting a good square wave pattern to figure out if its a bad sensor or if its further down stream, like the PCM.
Weird.... could be wiring, could be connector pins at the sensor and/or the PCM....
Good luck and keep us posted.
The engine runs flawlessly for an 40 min - hour not moving. I ran it with a cool breeze and it ran for over 2 but that may have been a fluke.
I do have an o-scope, albeit not an automotive but it is just fine to see the pulses.
I need to get at that sensor and look at it. I think if I am going to dig that deep, I should have a new one in hand and replace it good or bad. I already did the CKP.
I just wonder why it is reading a constant RPM.
It could be that something is disconnected and oscillating. The PCM's inputs are probably rock solid, outputs usually go.
Can't test it again, it is raining and may not heat enough.
1st Gear
Joined: Apr 2024
Posts: 1
Likes: 0
CMP Sensor always reads 1012 RPM on Tech 2
Well the problem is getting at the CMP it is buried, I haven't crawled underneath to see if I can get at it from there.
The engine runs flawlessly for an 40 min - hour not moving. I ran it with a cool breeze and it ran for over 2 but that may have been a fluke.
I do have an o-scope, albeit not an automotive but it is just fine to see the pulses.
I need to get at that sensor and look at it. I think if I am going to dig that deep, I should have a new one in hand and replace it good or bad. I already did the CKP.
I just wonder why it is reading a constant RPM.
It could be that something is disconnected and oscillating. The PCM's inputs are probably rock solid, outputs usually go.
Can't test it again, it is raining and may not heat enough.
The engine runs flawlessly for an 40 min - hour not moving. I ran it with a cool breeze and it ran for over 2 but that may have been a fluke.
I do have an o-scope, albeit not an automotive but it is just fine to see the pulses.
I need to get at that sensor and look at it. I think if I am going to dig that deep, I should have a new one in hand and replace it good or bad. I already did the CKP.
I just wonder why it is reading a constant RPM.
It could be that something is disconnected and oscillating. The PCM's inputs are probably rock solid, outputs usually go.
Can't test it again, it is raining and may not heat enough.
