Hey all I am having a problem with my 89 IROC. I keep getting the SES light from the EGR sensor. The problem is its new and the EGR switch that routs the vac. lines are also new. What do you think the problem could be. The car is running fine and getting good MPG. This problem only happens on long highway trips.


Thanks all
Brian

 

BTT

 

Brian, if you have a scan tool, you can monitor for the diag switch by unplugging it, then monitor to see if it intermittantly changess, which would indicate a wiring short somwhere

IIRC, this has happened after a cam swap? Recheck grounds, and wiring.

If I get some time later this evening, I'll look through my Helms

 

No it did it before also thats how I just got the new switch and valve. IS there any other parts to it. This problem only happens on highway driving.


Thanks for the help
Brian

 

You have an EGR vacuum solenoid valve, the EGR valve itself, and the EGR temperature diagnostic switch. The neutral safety switch is also involved, so that's another remote possibility.

If the ECM does not recieve a signal from the temperature switch when the EGR valve is supposed to open (at cruise) the ECM will set an error code.

Since you presumably have a new temperature switch, the EGR valve operation may be suspect. Without the correct operation of the exhaust backpressure pilot valve in teh EGR valve diaphragm, the valve won't open. Of course, the EGR passages in the intake base and valve base must be clean so that exhaust gasses can pass through.

Check the wiring to the temperature switch itself just to be sure the circuit is intact. Then you may need to cycle the valve through the diagnostic procedure to test the system.