My check engine light is on, and running diagnostics brings up code 71, "EGR temperature reporting too low."
I replaced the EGR valve with one from a crashed Corolla of the same year, which was far cleaner.
No light for an hour or so, but then it came right back on. The car needs emissions testing done, and won't pass with a check engine light, so if anyone knows how to fix this, any help would be appreciated.
Note - Something I've considered doing is replacing the EGR hoses as well, possibly they are clogged or filthy like the filter was?
A little more information would be helpful, like model year, model, where you are located, & mileage. Code 71 is pre-1996, and the presence of a code suggests that the vehicle is fuel-injected, but unfortunately, that is all I can deduce from the information you have provided so far.
Have you checked to make sure that there is not more than one code stored in the electronic control unit (ECU, A.K.A. "computer)?
If the only trouble codes is that EGR temperature is reporting too low, then the possible causes are a bad EGR temperature sensor, clogged EGR tube - (the metal one, not the rubber hose), or a leak in the EGR tube. Before you go and buy more parts, I would check to see if the EGR temperature sensor is putting out voltage.
It's a 1995 Corolla DX with 165,000 miles on the motor, 100,000 miles on the EGR valve. I'm located in Connecticut. It is fuel injected, and it burns oil unfortunately, if that makes a difference. And since I ran the diagnostics myself by jumping the terminals in the diagnostics box and checking the blinking check engine light, I really have no idea if there's more than one code.
If the engine is burning oil, the EGR valve and metal tube between the EGR valve and intake manifold can theoretically foul more quickly. Other consequences of oil burning are fouled spark plugs, fouled O2 sensors, and fouled catalytic converter. It is also possible that the EGR temperature sensor would become fouled.
When you pulled the diagnostic codes, if code 71 kept repeating, then that was the only code.
There are one or two electrical components to the EGR system - an EGR gas temperature sensor, and your car may or may not have an EGR valve position sensor. The EGR valve position sensor will be on the EGR valve itself and the EGR temp sensor will probably be in the tube between the EGR valve and the intake manifold.
The EGR temp sensor looks almost like a spark plug with 2 wires leading to a connector. Unplug the EGR temp sensor connector and measure the resistance between the 2 terminals with an ohm meter. It should read somewhere between
69 and 89 kilo ohm when the gas temp is around 100 degrees Fahrenheit, 11 -
15 kilo ohms at 212 degrees, and 2 to 4 kilo ohms at 300 degrees. If you want to check resistance at these temperatures, remove the sensor and stick the sensor end in a pan of oil and a thermometer. Gradually heat up the oil and take the resistance readings. If the end of the sensor is fouled with crud, cleaning the crud may cure the problem. If the tube between the EGR valve and the intake valve is fouled, you can try cleaning it with a wire brush that plumbers use to clean pipes or you can replace the tube.
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