GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Vivant 🢒 Transmission/Transaxle 🢒 Automatic Transmission - ZF 4HP 16 🢒 DTC P1871

Circuit Description

The pressure control solenoid (PCS) valves 3, 4, 5, and 6, are precision electronic pressure regulators that control the operation of the clutches, the brakes, and the lock-up clutch.

The valve reduces the system pressure with which the downstream solenoid valves and electrical pressure regulating valves are supplied. 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 applied to the high side driver is higher than the threshold, 6 V, with the high side driver switch OFF status, then a fault is detected.
    • No DTC P1870 is set.

Action Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will illuminate.
    • The transmission 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 the ignition is OFF/ON: 3rd gear by hydraulic control. Possible 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 lamp 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 P1871 sets, the possible cause of the fault could be the PCS valve power supply line.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Automatic Transmission?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

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

Are the amperes within the specified values?

0-2 A

Go to Diagnostic Aids

Go to Step 3

3
  1. Turn the ignition OFF.
  2. Disconnect the transaxle wiring connector and the transmission control module (TCM) connector.
  3. Measure the voltage of the transaxle wiring terminal 5.

Is the voltage within the specified values?

11-14 V

Go to Step 4

Go to Step 5

4

Replace the circuit for a short to power.

Did you complete the replacement?

--

System OK

--

5
  1. Remove the oil pan.
  2. Disconnect the PCS valve wiring connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage of the PCS 3 terminal 2.
  5. Measure the voltage of the PCS 4 terminal 2.
  6. Measure the voltage of the PCS 5 terminal 2.
  7. Measure the voltage of the PCS 6 terminal 2.

Is the voltage within the specified values?

11-14 V

Go to Step 6

Go to Step 7

6

Repair the circuits, power supply lines, for a short to power.

Did you complete the repair?

--

System OK

--

7

Replace the TCM. Refer to Transmission Control Module Replacement .

Did you complete the replacement?

--

Go to Step 8

--

8
  1. Clear the DTCs with a scan tool.
  2. Road test the vehicle.
  3. Observe the DTC information with a scan tool.

Are there any DTCs displayed that have not been diagnosed?

--

Go to Step 2

System OK