C - Testing Notes

DESCRIPTION
Reference Voltage (VREF) is a positive voltage (about 5.0 volts) that is output by the Powertrain Control Module (PCM). This consistent voltage is used by all 3-wire sensors.

Signal Return (SIG RTN) is a dedicated ground used by most Electronic Engine Controls (EEC) sensors and some other inputs.

NOTE
You should enter this pinpoint test only when a check for VREF has failed in the sensor Pinpoint Tests (D-Series) or Pinpoint Tests AA, AB, AC, or QA.

REMEMBER
This pinpoint test is intended to diagnose only the following:

- Sensor harness circuits: SIG RTN, VREF

- Three-wire sensors:
- Throttle Position (TP)
- EGR Valve Position (EVP)
- Pressure Feedback EGR (PFE)
- Differential Pressure Feedback EGR (DPFE)
- Manifold Absolute Pressure (MAP)
- Barometric Pressure (BARO)

- PCM