Crankshaft Position Sensor

[springfield]

I am not having any problems yet, but I do alot of out of state towing. Does any body know if the crank shaft position sensor problems of the 8.1 where only found in the 01 and 02s? Just wondering if the newer ones had an updated part and didn't see the problems. A little prevenative work goes a long way to save big headaches later!

 

Thanks

[[email protected]]

I am not having any problems yet, but I do alot of out of state towing. Does any body know if the crank shaft position sensor problems of the 8.1 where only found in the 01 and 02s? Just wondering if the newer ones had an updated part and didn't see the problems. A little prevenative work goes a long way to save big headaches later!

 

Thanks

 

I heard of the 03's and 04's doing it over on the avalanche forum. As 2500 avalanches have only 8.1l engines, I would think it was still a problem in 2004.

[zoney]

I have a 2001 8.1 engine that has a code that says the cam shaft sensor is faulty. I have replaced the sensor it worked fine for about three times of starting and stopping the engine and the service engine light came on and was back to the same problem. Have determined that there is low voltage getting to the sensor. Any ideas where the problem might be?? Even the mechanics are scratching their heads over this one.

[oldscsc]

I have a 2001 8.1 engine that has a code that says the cam shaft sensor is faulty. I have replaced the sensor it worked fine for about three times of starting and stopping the engine and the service engine light came on and was back to the same problem. Have determined that there is low voltage getting to the sensor. Any ideas where the problem might be?? Even the mechanics are scratching their heads over this one.

To clarify: you're saying the supply voltage going to the sensor isn't to spec? What is its voltage reading and what is spec?

[zoney]

The voltage is around 4 and spec I believe is around 11 volts. They say there is not enough power to the sensor.. It appears to be a somewhat intermittent problem. We had an improvement when we first put the sensor in. There was a slight hesitation on acceleration but otherwise appeared ok as the service engine light did go out. After three starts and stops the light came back on and we were right back to square one?????

[oldscsc]

11 volts seem high as sensors' normal reference voltages are 5V. The reasoning behind the low voltage is that a weak battery may not be able to produce 11-12V and the sensor data is necessary to start the engine. I would suggest figuring out the spec 100% for sure before going any farther.

 

If the spec actually is 11V and you're only getting 4V, you need to check the wiring going from the sensor to supply source and the sensor to ground. Likely, you have high resistance somewhere along the way. i.e. a loose fitting connector, corrosion on terminals, a dirty or loose ground etc.

[zoney]

The Techs now tell me the problem is a fuel pump. It is flowing at 25 psi and they tell me it needs to flow at 50 psi. Ummmm??? Low voltages makes sense yet they were trying to tell me it needed more voltage. Ummmm Hope they are right with the fuel pump. Tired of them guessing what the problem is and spending needless time at 90 dollars an hour

[oldscsc]

Get a fuel pressure gauge and hook it up to the Schrader valve on the fuel rail. Needs to read 55-62 key on, engine off. That is, assuming the 8.1 uses the same fuel pressure as the 4.8, 5.3, and 6.0.

 

If it doesn't reach 55 PSI, you have a weak pump, a leak in the system, or a fuel pressure regulator issue. If it reads higher than 62 PSI, you have a restriction somewhere in the system or a fuel pressure regulator issue.