GM/Detroit 6.5L – Engine Management – EGR CONTROL – Component Operation


The EGR control pressure/baro sensor is mounted on the left side of the cowl (figure 5-48). The sensor produces a voltage signal in proportion to the amount of absolute pressure in the EGR vacuum line. The PCM compares this actual signal to the desired EGR value it has calculated and makes minor corrections in EGR solenoid operation to compensate for the difference. If the difference between actual and desired EGR is too great forthe PCM to correct, a diagnostic trouble code will set. A Baro reading is taken on key up and when EGR is “OFF.”

EGR Control Pressure/Baro Sensor Circuit Operation

The EGR control pressure/baro sensor receives a 5 volt reference signal from the PCM on CKT 416 (figure 5-49).
This reference signal is shared with the crankshaft posi­ tion sensor and boost sensor. Based upon EGR vacuum, the sensor sends a signal back to the PCM on CKT 433.
Ground for the sensor is provided on CKT 452.

DTC 31 — “EGR Control Pressure/Baro Sensor Circuit Low (High Vacuum)”
DTC 31 sets when actual EGR pressure is less than 15 kPa for 2 seconds. Under these conditions, the PCM will shut down the EGR system.

DTC 33 — “EGR Control Pressure/Baro Sensor Circuit High (Low Vacuum)”
DTC 33 will set when the EGR vent is off and actual EGR pressure is more than 60 kPa higher than desired EGR.


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