Test Notes

EPR And Related Components:

OUTPUT FUNCTIONS
The Exhaust Back Pressure Regulator (EPR) is a variable position valve that controls exhaust back pressure during cold ambient temperatures to increase cab heat and decrease the amount of time needed to defrost the windshield. The Powertrain Control Module (PCM) uses the measured exhaust back pressure, intake air temperature and engine load to determine the desired exhaust back pressure.

Valve position is controlled by switching the output signal circuit to 12 volts inside the PCM. On/off time is dependent upon the exhaust back pressure.

Test Schematic:

DETECTION/MANAGEMENT
An open or shorted to ground control circuit can be detected by an on-demand output circuit check performed during the Key On Engine Off (KOEO) test.

An exhaust back pressure step test, in which the PCM commands and then measures specific preprogrammed pressures, is performed during the Key On Engine Running (KOER) test.

If the PCM detects an Exhaust Back Pressure (EBP) or Intake Air Temperature (IAT) sensor fault it will disable the exhaust back pressure device.





Harness Connector Checks To Ground (B-)
Check with regulator connector disconnected.





Harness EPR Voltage Check
Check with regulator and Engine Oil Temperature (EOT) sensor connector disconnected.





Harness Resistance Checks
Check with Breakout Box installed on harness only.

NOTE: After removing connectors, always check for damaged pins, corrosion, loose terminals, etc..

DTC DESCRIPTION
0475 = Exhaust pressure control valve malfunction.
0476 = Exhaust pressure control valve performance.