Chart C-2 MAP Sensor Check: VIN N (5.7L) VIN T (4.3L)

Fig. 026 - WIRING DIAGRAM for Chart C-2 MAP Sensor Check. VIN N, VIN T:

CHART C-2

MAP SENSOR CHECK

(FROM CODE 53 EGR CONTROL ERROR)

4.3L VIN "T"

5.7L VIN "N"

An Absolute Pressure Sensor (MAP) is used to monitor vacuum in the EGR vacuum circuit. It also sends the ECM a barometric pressure (altitude) signal when the ignition switch is on without the engine running or with the engine running when EGR is not in operation. This Baro signal allows the ECM to control altitude related injection pump timing the metering valve travel at W.O.T. The Baro signal is also used by the ECM along with absolute EGR control pressure, coolant temperature, metering valve position, TCC state, vehicle MPH and engine RPM to determine and control the EGR PWM duty cycle.

Fig. 025 - Chart C-2 MAP Sensor Check.:

1. Checks for V-ref. at MAP sensor harness. Normal voltage at Terminal "C" of MAP harness should be about 5 volts.
2. Checks for an open to ground in the MAP circuit to the ECM. Normal voltage is about 5 volts with a good ground.
3. Checks for proper circuit from the MAP signal wire to ECM Terminal "P" Incorrect voltage is an open or grounded wire, or faulty MAP sensor. Normal voltage by altitude is shown on table at bottom of chart.