Can the TPS be related to an EGR problem?


#1

Can TPS and EGR problems be related? The reason I ask is my SES light has been on for some time now giving a code for the EGR valve. I have replaced the valve and tube twice now with no fix, however, when I did replace it, it fixed an issue I was having with the Service Traction Control/Stabilitrak error message coming on. I just received a letter from GM stating that the TPS in some of the 2008 Chevy Equinoxes needs to be replaced and will be covered. They are very vague though at the problems you may be having in relation to the TPS and I don’t want to pay them $110 just to tell me that the TPS is not the issue.


#2

They are not related. But back to your EGR problem. In addition to the EGR valve and the tube, there are passages molded into the intake and exhaust manifolds that the exhaust gasses must pass through. These can get clogged up. Quick fix is to get a can of spray carburetor cleaner (i.e. Gumout) and attach the little hose to the sprayer. Stick it into each of the passages and spray until you stop getting spray back. Pulse spray, not continuous.


#3

Good advice by Keith above. One thing I like to do if I think my Corolla’s EGR valve is on the fritz is check to make sure it will stall the engine at idle when activated with a hand-held vacuum pump. If it is working and moving freely, it should.

On modern vehicles the EGR function is pretty complicated. The EGR valve is just a part of the EGR system. The system is set up so the EGR is only activated only when it should be for emissions purposes, and not activated when it shouldn’t be. The system often involves temperature sensors and vacuum activated sensors and electrical solenoids activated by the ECM, which in turn is reading coolant temperatures, transmission sensors, rpm sensors, mixture sensors, and vehicle speed sensors. So it is possible the EGR valve is ok, but something else in the loop is not working. I would have to disagree a bit with Keith’s comment that the TPS isn’t related. It probably isn’t, but since the TPS is read by the ECM, it could possibly be used in the ECM’s algorithm as to when to activate the EGR. Suggest to ask the dealership shop about that possibility.

I think the traction control/stability light comes on anytime the check engine light (or SES) comes on. It’s best to figure out why the SES is coming on first, as fixing that may turn off the stability light.


#4

If GM has a recall or shop notice currently for that vehicle. Its very difficult to say how the TPS can directly or indirectly affect the EGR…but GeorgeSJ makes a good point that it does use the TPS in complex algorithms on when to trigger an EGR open event…that statement is absolutely correct. If GM put that TPS notice out there… It does make you wonder. See how much the part is and install it yourself.

If I were you after I pulled all the codes from the ECU…I would do a Hard Reset on this car…Disconnect the battery for 15 minutes or so and reconnect. This resets all ECU’s and forces a “Re-Learn” on basically everything. Sometimes this is very helpful.

Blackbird.