P0870
P0870 - OD Hydraulic Pressure Test
For a complete wiring diagram, refer to.
Theory of Operation
Pressure switches are normally open (off or no pressure applied) and read high (+12 volts). When an element is applied, the corresponding pressure switch closes to ground (0.0 volts) or turns on. The controller tests the OD pressure switch when it is open (when the corresponding friction element is not applied) by briefly applying the OD element which will cause the corresponding pressure switch to close. The test verifies that the switches are operational and that the switch will close when the corresponding element is applied. If a switch fails to respond to two consecutive tests, the transmission system defaults to limp-in mode and illuminates the MIL.
• When Monitored: In any forward gear with engine speed more than 1000 rpm, shortly after a shift and every minute thereafter.
• Set Condition: After a shift into a forward gear, with engine speed greater than 1000 rpm, the PCM momentarily turns on element pressure to the clutch circuits that don't have pressure to identify the correct pressure switch closes. If the pressure switch does not close 2 times the DTC sets.
Always perform the pre-diagnostic troubleshooting procedure before proceeding. Refer to => Non-DTC Based Diagnostics. Pre-Diagnostic Troubleshooting Procedure
Test Step 1 - Checking for Loss of Prime DTC
• With the scan tool, read DTCs.
Is the DTC P0944 present also?
Yes
• Refer to the transmission category and perform the appropriate diagnostic procedure.
No
• Go to Test Step 2.
Test Step 2 - Check for Related Transmission DTCs
• With the scan tool, read DTCs.
Are any of the DTCs P0732, P0734 and/or P0846 present also?
Yes
• Replace the transmission solenoid/TRS assembly.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 3.
Test Step 3 - Determine if DTC P0870 is Current
• With the scan tool, read DTCs.
Is the status active for this DTC or is the STARTS SINCE SET counter 2 or less?
Yes
• Go to Test Step 4.
No
• Go to Test Step 9.
Test Step 4 - Check the PCM and Wiring with the Transmission Simulator
The starter solenoid relay must be removed from the TIPM. Failure to do so can result in personal injury or death.
Removal of the starter solenoid relay from the TIPM will prevent the vehicle from being started in gear.
• Turn the ignition OFF to the lock position.
• Remove the starter solenoid relay from the TIPM.
• Install the transmission simulator, Miller tool #8333 and the electronic transmission adapter kit.
• Ignition ON, engine not running.
• With the transmission simulator, turn the pressure switch selector switch to OD.
• With the scan tool, monitor the OD pressure switch state while pressing the pressure switch test button on the transmission simulator.
• Wiggle the wires leading to the PCM while pressing and holding the pressure switch test button.
Did the OD pressure switch state change to closed and remain closed while wiggling the wires?
Yes
• Disassemble and inspect the valve body and repair or replace as necessary. If no problems are found in the valve body, replace the transmission solenoid/TRS assembly.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 5.
Test Step 5 - Check the OD Pressure Signal Circuit for an Open
Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.
• Turn the ignition OFF to the lock position.
• Disconnect the PCM C4 harness connector.
• Disconnect the transmission solenoid/TRS assembly harness connector.
• Measure the resistance of the OD pressure signal circuit between the appropriate terminal of Miller tool #8815 and the transmission solenoid/TRS assembly harness connector.
Is the resistance more than 5.0 ohms?
Yes
• Repair the OD pressure signal circuit for an open.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 6.
Test Step 6 - Check the OD Pressure Signal Circuit for a Short to Ground
• Measure the resistance between ground and the OD pressure signal circuit.
Is the resistance less than 5.0 ohms?
Yes
• Repair the OD pressure signal circuit for a short to ground.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 7.
Test Step 7 - Check the OD Pressure Signal Circuit for a Short to Voltage
• Ignition ON, engine not running.
• With the scan tool in the TIPM, actuate the TCM output.
• Measure the voltage of the OD pressure signal circuit.
Is the voltage more than 0.5 volts?
Yes
• Repair the OD pressure signal circuit for a short to voltage.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Go to Test Step 8.
Test Step 8 - Check the Transmission Control Output Circuit or an Open
• While still actuating the TCM output in the TIPM with the scan tool, and using a 12 volt test light connected to ground, check transmission control relay output circuit in the transmission solenoid/TRS assembly harness connector.
• The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.
Does the test light illuminate brightly?
Yes
• Using the schematics as a guide, check the powertrain control module terminals for corrosion, damage, or terminal push out. Pay particular attention to all power and ground circuits. If no problems are found, replace and program the PCM per the. Refer to With the scan tool, perform Quick Learn.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Repair the transmission control output circuit for an open.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
Test Step 9 - Intermittent Wiring and Connectors
• The conditions necessary to set the DTC are not present at this time.
• Using the schematics as a guide, inspect the wiring and connectors specific to this circuit.
• Wiggle the wires while checking for shorted and open circuits.
• With the scan tool, check the DTC event data to help identify the conditions in which the DTC was set.
Were there any problems found?
Yes
• Repair as necessary.
• Perform the Transmission Verification Test. Refer to => Non-DTC Based Diagnostics. Transmission Verification Test
No
• Test Complete.