The pressure switch manifold (PSM) is a multiple-switch assembly made up of 3 normally open (N/O) pressure switches and 1 normally closed (N/C) pressure switch for reverse pressure. Fluid pressure is supplied to the pressure switch 4 (PS4) when the manual selector valve is in any position except REVERSE. When the manual selector valve is moved to REVERSE, pressure to PS4 is cut off, causing the switch to close.
DTC P0877 is a type B DTC.
This diagnostic procedure supports the following DTC:
DTC P0877 Transmission Pressure Switch 4 Circuit Low
• | The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts. |
• | Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds. |
• | The transmission fluid temperature (TFT) is greater than 0°C (32°F). |
• | DTC P0708 and P0878 is not active. |
DTC P0877 sets when P (PARK), N (NEUTRAL), or a forward range is selected and the PS4 state remains in the mechanically closed/electrically ON position for greater than 1.0 second.
• | The transmission control module (TCM) illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met. |
• | The transmission will lock in NEUTRAL. |
• | DTC P0877 is stored in TCM history. |
• | The TCM freezes shift adapts. |
• | The TCM inhibits torque converter clutch (TCC) engagement. |
A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.
• | Inspect the wiring for poor electrical connections at the TCM. Inspect 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 |
• | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
• | You may have to drive the vehicle in order to experience a condition. |
• | This DTC could indicate a hydraulic leak path exhausting pressure from the reverse PS4. |
The numbers below refer to the step numbers on the diagnostic table.
This step tests the TCM response function.
This step tests the transmission wiring harness integrity.
This step tests and evaluates the internal wiring harness.
This step tests the PSM for a failed condition.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Measure the transmission fluid level. Refer to Transmission Fluid Check . Is the transmission fluid level correct? | Go to Step 3 | Go to Transmission Fluid Check |
3 | Measure line pressure. Refer to Line Pressure Check . Is the line pressure within the specified value? | Go to Step 4 | |
4 |
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data. Does the scan tool indicate PS4 status is HIGH? | Go to Diagnostic Aids | Go to Step 5 |
Does the scan tool indicate PS4 status is LOW when grounded and HIGH when open? | Go to Step 6 | Go to Step 12 | |
Does the scan tool indicate PS4 status is LOW when grounded and HIGH when open? | Go to Step 7 | Go to Step 11 | |
Does the scan tool indicate PS4 status is LOW when grounded and HIGH when open? | Go to Step 8 | Go to Step 10 | |
Does the scan tool indicate PS4 status is LOW when grounded and HIGH when open? | Go to Step 9 | Go to Diagnostic Aids | |
9 | Replace the PSM. Refer to Pressure Switch Manifold Replacement . Did you complete the replacement? | Go to Step 13 | -- |
10 | Replace the AT internal wiring harness. Refer to Wiring Harness Replacement . Did you complete the replacement? | Go to Step 13 | -- |
11 | Test the PS4 circuit between the TCM and the AT inline 20-way connector for an open or short condition. Refer to Circuit Testing . Did you find and correct the condition? | Go to Step 13 | -- |
12 |
Important: Prior to replacing the TCM, swap the TCM with a known good TCM. In most cases, the TCM is not at fault. Investigate thoroughly before replacing the TCM. Replace the TCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 13 | -- |
13 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | Go to Step 14 | Go to Step 2 |
14 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display and DTCs that you have not diagnosed? | System OK |