Circuit Description
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. Pressure switch 3 (PS3) monitors shift valve 3 positioning and relays it to the transmission control module (TCM).
DTC P0873 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0873 Transmission Pressure Switch 3 Circuit High
Conditions for Running the DTC
| • | 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. |
| • | Shift valve 3 is commanded to the ON, stroked, position. |
Conditions for Setting the DTC
DTC P0873 sets during steady state operation when shift solenoid 3 (SS3) is commanded ON and PS3 fails to switch ON after 0.1 second.
Action Taken When the DTC Sets
| • | The TCM illuminates the malfunction indicator lamp (MIL). |
| • | When in a forward range and shifting is completed, the transmission will fail to another forward range, unless the transmission is compromised by overspeeding or direction change, then the transmission will shift to NEUTRAL. |
| • | When in a forward range and the shift is in process, the transmission will return to a previous range, except for 1-2 shifts and 2-1 shifts which will be completed. |
| • | When in NEUTRAL or REVERSE, the transmission will fail to NEUTRAL. |
| • | While diagnostic response is active, the shift selector is moved from a forward range to NEUTRAL or from a forward range to REVERSE, then the transmission will shift to NEUTRAL. |
| • | DTC P0873 is stored in TCM history. |
| • | The TCM freezes shift adapts. |
| • | The TCM inhibits torque converter clutch (TCC) engagement. |
Conditions for Clearing the DTC
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.
Diagnostic Aids
| • | 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. |
| • | When DTC P0761 and DTC P0873 are set in combination, this may indicate an open circuit condition is present in PS3. |
| • | This DTC may indicate that SS3 is mechanically defective. |
| • | This DTC can be caused by a loss of prime. |
Test Description
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 PS3 status is LOW? | Go to Diagnostic Aids | Go to Step 5 |
Does the scan tool indicate PS3 status is LOW when grounded and HIGH when open? | Go to Step 6 | Go to Step 15 | |
Does the scan tool indicate PS3 status is LOW when grounded and HIGH when open? | Go to Step 7 | Go to Step 14 | |
Does the scan tool indicate PS3 status is LOW when grounded and HIGH when open? | Go to Step 8 | Go to Step 13 | |
Does the scan tool indicate PS3 status is LOW when grounded and HIGH when open? | Go to Step 9 | Go to Step 12 | |
9 | Remove the control valve body and inspect for a stuck or sticking shift valve 3. Refer to Control Valve Body Assembly Disassemble . Was the shift valve 3 stuck or sticking? | Go to Step 11 | Go to Step 10 |
10 | Replace the SS3 and install the control valve body. Refer to Control Valve Body Replacement . Did you complete the solenoid replacement and installation of the valve body? | Go to Step 16 | -- |
11 | Clean and/or polish the sticking valve to restore free movement or replace the control valve body assembly. Refer to Control Valve Body Replacement . Did you restore free movement or replace the valve body? | Go to Step 16 | -- |
12 | Replace the PSM. Refer to Pressure Switch Manifold Replacement . Did you complete the replacement? | Go to Step 16 | -- |
13 | Replace the AT internal wiring harness. Refer to Wiring Harness Replacement . Did you complete the replacement? | Go to Step 16 | -- |
14 | Test the PS3 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 16 | -- |
15 |
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 16 | -- |
16 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | Go to Step 17 | Go to Step 2 |
17 | 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 | |
