Circuit Description
The Transmission Control Module (TCM) supplies 5 volts to the BARO sensor. As the atmospheric pressure changes the resistance within the BARO sensor also changes, modifying the voltage on the BARO sensor input signal. When atmospheric pressure is high, (100 kPa), input signal voltage will also be high (approx. 4.5 V). As atmospheric pressure decreases, so does the input signal voltage.
If the TCM detects a low voltage on the BARO sensor circuit, then DTC 64 sets.
Conditions for Setting the DTC
BARO sensor signal voltage less than 1.9 volts for greater than 2 seconds.
Action Taken When the DTC Sets
| • | The TCM does not illuminate the Malfunction Indicator Lamp (MIL). |
| • | No altitude compensation of shift patterns. |
| • | The TCM uses a default BARO value of 100 kPa. |
| • | DTC 64 is stored in TCM history. |
Conditions for Clearing the DTC
| • | The TCM clears the DTC from Current to History when the fault condition(s) no longer exist and the ignition switch is cycled OFF and then ON. |
| • | A scan tool can clear the DTC from Current and History status. The TCM clears the DTC from the TCM history if the vehicle completes 40 ignition cycles without a failure reported. |
| • | The TCM cancels the DTC default actions when the fault no longer exists and the ignition is cycled OFF and then ON. |
Diagnostic Aids
| • | Inspect the wiring at the TCM, the transmission connector and all other circuit connecting points for the following conditions: |
| - | A bent terminal |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| • | If the DTC will not set, use snapshot mode on the scan tool to trigger ON this DTC, then review data to identify source. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step verifies the 5 volt supply to the BARO sensor.
-
This step verifies a good BARO sensor ground circuit 452.
-
If the entire circuit is OK, the voltage measured will be approximately 5 volts.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Were you sent here from the "Powertrain On-Board Diagnostic (OBD) System Check?" | -- | ||
Is the voltage within the specified values? | 4.7 - 5.3 v | |||
Using a test light connected to B +, probe ground circuit 452 at the BARO sensor connector. Is test light ON? | -- | |||
Is the voltage greater than 4.7 volts? | -- | |||
5 | Verify proper terminal tension at the BARO sensor connector. Was the condition found and corrected? | -- | ||
6 | Replace the BARO sensor. Refer to Barometric Pressure Sensor Replacement . Was the BARO sensor replaced? | -- | -- | |
7 | Repair the open in the ground circuit 452 from the BARO sensor to the TCM. Refer to Wiring Repairs . Was the open repaired? | -- | -- | |
8 | Repair the 5 volt reference circuit 416 to the BARO sensor. Refer to Wiring Repairs . Was the circuit repaired? | -- | -- | |
9 | Inspect circuit 433 for an open or a short to ground. Refer to General Electrical Diagnosis . Was the condition found and corrected? | -- | ||
10 | Replace the TCM. Refer to DTC 51 PROM Error TCM Replacement. Was the TCM replaced? | -- | -- | |
11 | In order to verify your repair, perform the following procedure:
Is the J 39200 DMM voltage within the specified value? | 1.9 - 4.9 volts | System OK | Begin diagnosis again |
