Pinpoint Test M: Exhaust BACKPRESSURE Regulator: Description
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 amount of time needed to defrost windshield. Powertrain Control Module (PCM) uses measured exhaust back pressure, intake air temperature and engine load to determine desired exhaust back pressure. Valve position is controlled by switching output signal circuit to 12-volts inside PCM. ON/OFF time is dependent upon exhaust back pressure. An open or shorted to ground control circuit can be detected by a KOEO OUTPUT STATE SELF-TEST. See KOEO OUTPUT STATE SELF-TEST under QUICK TEST. An exhaust back pressure step test, in which PCM commands and then measures specific preprogrammed pressures, is performed during KOER test. If PCM detects an Exhaust Back Pressure (EBP) or Intake Air Temperature (IAT) sensor fault, it will disable exhaust back pressure device. DTC 0475 indicates exhaust pressure control valve malfunction. DTC 0476 indicates exhaust pressure control valve performance.
Perform this test when directed here by QUICK TEST. This PINPOINT TEST is intended to diagnose:
- Exhaust Back Pressure Regulator (EPR).
- Wiring harness circuits; (PWR GND and EPR signal).
- Powertrain Control Module (PCM).