Bad ECM or bad EGR?
 

Hi, I have a 1992 S-10 Blazer with a 4.3L Vortec and CPFI, and my check engine light is on. The only DTC code is 32 (EGR valve or MAP sensor failure). I've changed the MAP sensor, cleaned the exhaust passages in the intake manifold and cleaned the EGR valve thoroughly, but code 32 keeps coming back. :icon_doh: I know the ECM controls the EGR valve and I seem to have some incorrect voltages at the valve. Both pintle solenoid wires stay at 12 volts (the ECM is supposed to pull one side low to make the pintle move). Also, the pintle position sensor signal wire stays at 0.07 volts. These voltages tell me that the pintle isn't moving. Is the ECM the most likely culprit or could something else be to blame? I believe the EGR valve is good and the ECM is bad, I can apply 12 volts to the solenoid wires with the valve on the bench and the pintle moves as it should. The position sensor checks okay on the bench too, I measure about 5k ohms between terminals B and D and the resistance at terminal C changes when I move the pintle manually.

By the way, I made a block off plate when I thought the EGR valve might be bad. Since I can't afford a new EGR valve right now, will it hurt anything to drive the Blazer with the CEL on and the block off plate installed? Any help is appreciated.

I take the lack of responses to mean this isn't a common problem. :( I'll ask the question another way: Is a bad ECM the most likely cause of incorrect voltages at the EGR valve?

https://blazerforum.com/forum/attach...ine=1378310352

Pins A and E are always high, pin C is always low.This tells me the pintle isn't moving.

Anyone... anyone... Bueller... anyone? Did I post this in the wrong forum? I'd really like some opinions on this problem before I buy an ECM that I may not need.

Does anyone have a GUESS why the ECM isn't commanding the pintle to move? When I disconnect the battery to clear the codes, then reconnect it and start the engine, the CEL comes on within a few seconds. Unless I'm mistaken, the ECM is supposed to command the pintle to move and the MAP sensor is supposed to register a change in pressure. If these events fail to occur, the ECM sets a Code 32. Can anyone confirm this?

before replacing the ecm which is a incommon issue,put power to the egr. If anything go to the yard and get a used one. egrs are prong to fail. computers can too but its rare. id look into simple things before doing that.

I've already applied power to the solenoid wires (A and E) with the valve on the test bench and the pintle moved in & out like it should. In fact I cycled it dozens of times while I was cleaning the valve.

I've already checked the "simple things" and documented my findings in my first two posts. I need to know what conditions must be met before the ECM will pull Pin A low and energize the solenoid, since that isn't happening. I also need to know if 5k ohms between Pins B and D is a normal resistance measurement.

I'm really hoping someone will tell me about an oddball left-field problem that can prevent the ECM from energizing the EGR solenoid, otherwise I'm going to have to order an ECM and hope for the best.

BTW, the yards around me don't have any Blazers older than 1999, I already checked. Thanks for the suggestion though.