Help with engine codes 94 Grand Am

Also wanted to add that they replaced map sensors but to no avail.

(when in doubt...) Have you cleaned the EGR passages?

Might be an intermittant vacuum leak. (33 and 34 are MAP high Voltage and MAP low voltage)

GW

KDawg wrote:

Code 51 basically means some kind of internal failure within the ECM. If it's not the PROM, it's likely the ECM itself.

Code 33 is "MAP sensor signal voltage was too high (low vacuum) for 4 seconds when throttle angle was between 3% and 30% and held steady." Code 34 is "MAP sensor signal voltage was too low (high vacuum) for 2.5 seconds when engine speed was above 500 RPM."

Often when you have contradictory trouble codes set like those two, that tends to point towards a bad ECM as well..

They said they checked for vacumm leaks and found no problems. They also replaced the map sensor, and did O2 sensor as well. Replaced the prom, but I'm not sure if that is the same thing as replacing the ECM.

I unhooked the battery last night for about 45 minutes. Hooked it back up, and took it out for a test. I though the problem had vanished cause it did not happen for over an hour of driving and testing under the conditions that would usually flag the sensors. Then it finally came on later last night.

The PROM is just a chip or module that plugs into the ECM.