EGR problems continue

[Yarls24]

I've changed the egr temp. switch, and now the egr solenoid. That service engine light continues to come on afer about 10 to 20 miles of highway driving. What do I do next? Is the egr valve bad? Can you clean it without taking it off? I don't know where to turn next.

 

[JonM]

What happens when you have the car running and you push up on the diaphram on the EGR? It should almost try to stall. You can remove it and clean it, just be careful you do not break any bolts.

 

[Chick]

You have to take the plenum off, then you can take the egr off to inspect and clean it.

Here are some procedures for testing. It will guide you on how to test related circuts too.
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CODE 32 - EXHAUST GAS RECIRCULATION (EGR) CIRCUIT

Circuit Description:
The Exhaust Gas Recirculation (EGR) valve vacuum is controlled by an Electronic Control Module (ECM) controlled solenoid. The ECM will turn the EGR "ON" and "OFF" (Duty Cycle) by grounding CKT 435. The duty cycle is calculated by the ECM based on information from the coolant and mass air flow sensor and engine rpms. There should be (NO EGR) when in park or neutral, Throttle Position Sensor (TPS) input below a specified value, or TPS indicating Wide Open Throttle (WOT). With the ignition "ON," engine stopped, the EGR solenoid is de-energized and, by grounding the diagnostic terminal, the solenoid is energized.

Test Description: Numbers below refer to circled numbers on the diagnostic chart.

Code 32 means that the EGR diagnostic switch was closed during start-up or that the switch was not detected closed under the following conditions:

Coolant temperature greater than 92C (176 degrees F)
EGR duty cycle commanded by the ECM is greater than 75%
TPS less than 1/2 throttle, but not at idle

Codes 21, 22, 33 & 34 not present

All conditions above must be met for about 4 minutes

If the switch is detected closed during start-up, or if the switch is detected open when the above conditions are met, the "Service Engine Soon" (SES) light will remain "ON," unless the switch changes state.

This test will determine if the ECM set the code due to CKT 935 being grounded on start up. If the "Scan" does not indicate the switch is closed, but the customer complained of a "Service Engine Soon" light after start up, then this circuit should be checked carefully for an intermittent grounded condition,
If the "Scan" indicates the switch is no longer closed after disconnecting it, be sure the switch is not closed due to heat. (EGR being "ON" prior to test.)

This test will check for a possible open in CKT 935. The ECM supplies 9-12 volts to CKT 935 and the "Scan" should indicate switch being closed when CKT 935 is grounded.

By grounding the diagnostic terminal, the EGR solenoid should close, and allow vacuum to be applied and the vacuum should hold.

This test will determine if the electrical control part of the system is at fault, or if the connector or solenoid are at fault.
By plugging the EGR valve side and ungrounding the diagnostic terminal, the solenoid valve should open and allow vacuum to bleed off through the vent.

With the engine not running and vacuum is applied to the valve, the valve should move to the fully open position.
Due to this engine using a negative back pressure valve, the valve should close when the engine is cranked over.

 

[Yarls24]

Thanks Jon M. and Chick. I will try the vacuum test and see what happens. I am dreading taking off the plenum and replacing the egr valve. Chick, thanks for the great testing proceedure diagram. I will keep you posted on the outcome.