GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Vivant 🢒 DTC 🢒 DTC P1870

Circuit Description

The pressure control valve, PCS valve 3, 4, 5, 6, is a precision electronic pressure regulator that controls the operations of each clutch, brake, and lock-up clutch.

The valve reduces the system pressure with which the downstream solenoid valves and electrical pressure regulating valves are charged. It is possible to use smaller solenoid valves as a result. The PCS requires a constant input pressure.

Conditions for Setting the DTC
    • If the voltage on the ignition voltage applied to the high side driver is lower than the value that subtracts the constant value, 3.5 volts, to detect a shortage to ground from the ignition voltage, then a fault is detected.
    • DTC P1871 is not set.

Action Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will illuminate.
    • The transaxle control module (TCM) will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffer.
    • Adopt Emergency/Substitute Mode and constant 4th gear by hydraulic control.
    • After ignition OFF/ON, 3rd gear by hydraulic control--P, R, and N are also possible.
    • The power supply is cut off to the PCS valve.

Conditions for Clearing the MIL/DTC
    • The MIL will turn OFF when the malfunction has not occurred after 3 ignition cycles.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • Using a scan tool can clear history DTCs.

Diagnostic Aids

When DTC P1870 sets, the repair of the PCS valve power supply line is recommended.

Step

Action

Values

Yes

No

1

Perform the Diagnostic System Check.

Was the check performed?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2
  1. Install the scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Start the engine and allow it to warm up at idle.
  4. Put the gear selector in Park, Neutral, and set the parking brake.
  5. Observe PCS 3, 4, 5, 6 input ampere and output ampere on the scan tool.

Are the amperes within the specified range?

0-2 A

Go to Diagnostic Aids

Go to Step 3

3
  1. Turn the ignition to LOCK.
  2. Disconnect the transaxle wiring connector and transaxle control module (TCM) connector.
  3. Measure the resistance between terminal 5 of the transaxle wiring connector and C6 of the TCM wiring connector.
  4. Measure the resistance between terminal 5 of the transaxle wiring connector and C7 of the TCM wiring connector.

Is the resistance within the specified value?

0 ohms

Go to Step 5

Go to Step 4

4

Repair the circuit for a short to ground and an open.

Is the action complete?

--

System OK

--

5
  1. Remove the oil pan.
  2. Disconnect the PCS 3 wiring connector.
  3. Measure the resistance between terminal 5 of the transaxle wiring connector and 2 of the PCS 3 wiring connector.

Is the resistance within the specified value?

0 ohms

Go to Step 7

Go to Step 6

6

Repair the circuit, power supply lines, for a short to ground and an open.

Is the action complete?

--

System OK

--

7

Replace the TCM.

Is the action complete?

--

Go to Step 8

--

8
  1. After the repair, use the scan tool clear info function and road test the vehicle.
  2. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 2

System OK