DRIVE GP-FINAL 4552775 - Caterpillar

MID 087 - Chassis ECMCID 0849 - System Air Pressure SensorFMI 03 - Voltage Above Normal
Illustration 1 g01883713
System air pressure sensor circuit
This diagnostic code indicates the "Chassis" ECM detects the system air pressure sensor voltage is above normal.The pressure sensor has the following characteristics:
Is a pulse width modulation (PWM) sensor
Operating duty cycle from 0% to 100%
Operating pressure range from 0 kPa (0 psi) to 1135 kPa (164 psi)
Pressure and duty cycle relationship is linearThe following can cause this code:
Sensor signal circuit open
Sensor signal circuit shorted to the +battery circuit
Sensor failure
Power circuit failure
Ground circuit failure
ECM failureNote: The following test procedure may create other diagnostic codes. Ignore these created codes and clear these created codes after the original diagnostic code has been corrected. Ensure diagnostic code CID 0849 FMI 03 is active before performing this procedure.Note: Use a calibrated digital multimeter for this procedure.Test Step 1. CHECK FOR POWER AT THE SENSORDo not disconnect the harness connector from the sensor.
Turn on the disconnect switch and the key switch.
At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the voltage supply wire (contact A).
Measure the voltage from contact A to frame ground.Expected Result:The voltage is 8 0.5 VDC.Results:
OK - The voltage is 8 0.5 VDC. Proceed to Test Step 2.
NOT OK - The voltage is not 8 0.5 VDC. The circuit is open. Proceed to Test Step 5.Test Step 2. CHECK FOR SENSOR GROUNDThe harness remains connected from the sensor.
Turn off the key switch and the disconnect switch.
Remove the 7X-1710 Multimeter Probe from the voltage supply wire (contact A).
At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the ground wire (contact B).
Measure the resistance from contact B to frame ground.Expected Result:The resistance is less than 5 ohms.Results:
OK - The resistance is less than 5 ohms. Proceed to Test Step 3.
NOT OK - The voltage is not 8 0.5 VDC. The circuit is open. Proceed to Test Step 5.Test Step 3. CHECK THE SENSOR SIGNAL CIRCUIT
Reconnect the harness to the ECM and sensor.
At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the signal wire (contact C).
At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the ground wire (contact B).
Turn on the disconnect switch and the key switch.
Measure the sensor signal.Expected Result:The sensor signal is as described at the beginning of this procedure.Results:
OK - The sensor signal is valid. Proceed to Test Step 4.
NOT OK - The sensor signal is not valid. The sensor has failed.Repair: Replace the sensor.STOPTest Step 4. CHECK THE SIGNAL CIRCUIT AT THE ECM
Turn off the key switch and the disconnect switch.
Insert the multimeter probes into the back of the ECM connector along J2-32 (wire M914-WH(White)) and J1-45 (wire C242-BK(Black)).
Turn on the disconnect switch and the key switch.
Monitor the sensor signal with a multimeter.
Without disconnecting the sensor or sensor hardware from the machine, take