Related Trouble Code Description

PURPOSE
Reduces NOx emissions and prevents spark knock.

OPERATION
The EGR system recirculates exhaust gases back through the intake manifold to help control combustion temperature and promote even flame distribution in the cylinder.

The EGR valve is controlled by manifold vacuum and exhaust backpressure through a solenoid/transducer. The Powertrain Control Module (PCM) controls the solenoid operation through cavity 35.

NAME OF CODE:
EGR System Failure

WHEN MONITORED:
With engine temperature greater than 140° F, engine in closed loop, O2 sensor operational, engine under a steady load with the throttle open, and adaptive memory not at or near its limits.

SET CONDITION:
Once all the conditions are met, the EGR is turned off and on momentarily. The oxygen sensor signal is monitored for changes in its output signal during this test. If no significant change is seen, a flag is set. The test is repeated up to 8 times in a run cycle. If the test fails every time, the code is set. If any of the tests Pass, the diagnostics are suspended for the run cycle.

POSSIBLE CAUSES:
- Open or blocked vacuum supply to the EGR valve
- Blocked exhaust transfer tubes to the intake manifold
- Blocked backpressure tube to the transducer
- Failed EGR valve
- Failed EGR solenoid/transducer
- EGR solenoid/transducer not positioned horizontal
- Failed PCM