I have a 94 camaro z28. I been having problems with a code which is DTC 21 - High voltage throttle sensor. It's currently reading .62 idle and 4.9 WOT. I heard on the 94 models it should not exceed 4.9 on WOT. I also heard it should not exceed 4.8 on WOT. I just basically want to know where to set the sensor at. Should it be at 4.8 or 4.9 on WOT?

 

Either should be fine. The PCM uses a 5v reference, so it can't be more than that.

 

I have a manual page, but it doesn't specify the year.... might be for a 93.

Not sure if this applies to your 94, but the point is to show that there is more than one diagnostic test run on TPS.

I also have the 96/97 charts, and that indicates that the OBD-II system simply check for voltage exceeding 4.9V for more than 1 second while the ignition is on, to set the code. But they changed a few things between OBD-I and OBD-II diagnostics. Best thing would be to ask if anyone has a 1994 manual, and can look up the diagnostic criteria for you.

Did you ever turn the ignition to "on", hook up a volt meter to the blue signal wire/black ground wire and slowly rotate the throttle blades, looking for "spikes" in the voltage?

Have you verified that the reference voltage (gray wire) is not excessive, and above 5.0V?

 

The 94 manual says DTC 21 will set when:

TPS signal is greater than 2.5v, engine idling (less than 10 grams/sec air flow), all conditions met for 5 seconds or TPS voltage over 4.8v with ignition ON.

So, WOT is not the only concern. The TPS should also be checked for a linear progression from throttle closed to WOT (engine does not have to be running for you to do this).

 

If you have access to an oscilloscope that would be your best tool for checking out that TPS. Regular multi-meters/volt-meters typically cannot refresh the data fast enough to pick up every area of the signal so you may miss a possible problem section.