I did do a search but wasnt able to find anything sssooo... A friend has a 2000 blaze thats not running right. The scanner told him the battery was bad, has vacuum leaks, & a bad cam position sensor. First are easy enough, but where could I find the cam sensor?

Jeremiah

 

It's in the distributor, take off a cap and rotor button it's will be the 1 with the wires attached at the back side of the distributor

 

Cause when I was rebuilding my engine I didnt see one.The only one I could think of was the one on the timing chain cover.

 

OK will check that tomorrow (ran out of daylight today). Now, does this include the models with the wires pointing straight out to the pass. & drivers sides? I ask because the haynes manuel showed 2 types of dizzy caps.

 

I know this it true for the (crab style) pointing out the.sides as you put it...which should be what you have I done this a few Weeks ago on a friends , it should not take very long to do I don't know your skill level but make sure you don't mix up your plug wires...lol

 

Trouble codes never tell you to replace parts. They tell you a problem was detected in a certain circuit. What was the DTC? If it does turn out to be the camshaft position sensor needing replacement, camshaft retard must be checked/adjusted after replacement.

 

Capt. hook, how do you adjust the cam retard?

I have been around the block a few times (I've been professionally building custom cars for over 10 years). lol. Though I specialize in gm fwd, I've been through a blazer/ jimmy more than once.

 

Camshaft retard is viewed on a scan tool capable of accessing it. The el cheapo $300 or $400 scan tools can't access it, gotta be a higher end tool. Camshaft retard is adjusted by rotating the distributor. It affects base ignition timing as well as aligning the sensor with the camshaft, (hence the name, "camshaft position sensor"). It also perfectly aligns the rotor segment with the terminals on the distributor cap to reduce or eliminate crossfire inside the cap. The crankshaft position sensor data, along with the camshaft position sensor data, is used by the PCM for accurately detecting and identifying cylinder misfire. Unlike the crankshaft position sensor, if camshaft position sensor data is not received by the PCM, (ie. sensor unplugged) the PCM substitutes a default value and the engine will continue to run. If crankshaft position sensor data is not received, the engine will not run. Spec for camshaft retard is zero degrees, (desired) with a tolerance of plus or minus 2 degrees at 1500 RPM, or above.

 

Interesting, but wouldnt a basic timing check/ alignment work just as well?

 

Nope. Timing lights are obsolete on this engine. The PCM uses crankshaft position sensor data to determine the exact position of the crankshaft. The PCM applies the proper amount of ignition timing advance to the ignition module, which in turn fires the ignition coil. The amount of advance that the PCM is applying is viewed on the scan tool. If the PCM applies +10 degrees advance, and camshaft retard is -10 degrees, the spark plugs are firing when the pistons are at TDC. The PCM has no way of "knowing" where camshaft retard is set, so it assumes that it's correct. It's up to the technician to make sure it's adjusted properly. On older vehicles, base ignition timing was set either by disabling vacuum and centrifugal advance, or disconnecting the EST, (Electronic Spark Timing) circuit, and using a timing light. On this engine, what equates to "base timing" is called camshaft retard. This is why it's so important that it's correct. Camshaft retard can be off as much as ~27 degrees either way, and NOT set a DTC in memory. 27 degrees off! Tell me THAT won't affect performance