GM Service Manual Online
For 1990-2009 cars only

DTC P1861 Non-Europe or N. American Emissions

Circuit Description

The pressure control valves 3, 4, 5, and 6 are precision electronic pressure regulators that control the operation of the clutches, brakes, and 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 pressure control valves require a constant input pressure.

Conditions for Setting the DTC

    • Output voltage of the solenoid valve 4 is less than 2 volts.
    • No DTC P1862, P1863.
    • Immediately after the above condition occurs

Action Taken When the DTC Sets

    • The hold lamp will blink.
    • 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 ignition OFF/ON: 3rd gear by hydraulic control. Possible P, R, and N also possible.
    • Power supply cut off to the pressure control solenoid valve.

Conditions for Clearing the Hold Lamp/DTC

    • The hold 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 P1861 sets, the possible cause of fault could be the pressure control valve 4.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select Actuating on the scan tool.
  4. Actuate pressure control valve 4 ON/OFF.

Does the valve change ON/OFF?

--

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn the ignition OFF.
  2. Disconnect the transaxle wiring connector.
  3. Measure the resistance between terminals 5 and 7 of the transaxle wiring connector.

Is the resistance within the specified value?

TFT 25°C (77°F)

6 ohms

Go to Step 7

Go to Step 4

4

  1. Remove the oil pan.
  2. Disconnect the wiring connector of pressure control solenoid valve 4.
  3. Measure the resistance between terminal 2 of the solenoid valve 4 and ground.
  4. Measure the resistance between terminal 1 of the solenoid valve 4 and ground.

Is the resistance within the specified value?

Go to Step 6

Go to Step 5

5

Repair the internal line for valve 4 for a short to ground.

Is the repair complete?

--

System OK

--

6

Replace solenoid valve 4.

Is the replacement complete?

--

System OK

--

7

  1. Disconnect the transaxle wiring connector and transmission control module (TCM) connector.
  2. Measure the resistance between terminal 5 of the transaxle wiring connector and ground.
  3. Measure the resistance between terminal 7 of the transaxle wiring connector and ground.

Is the resistance within the specified value?

Go to Step 9

Go to Step 8

8

Repair the transaxle wiring harness for a short to ground.

Is the repair complete?

--

System OK

--

9

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the replacement complete?

--

Go to Step 10

--

10

  1. After the repair, use a scan tool Clear Info function and road tests the vehicle.
  2. Review the DTC Info.

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

--

Go to Step 2

System OK

DTC P1861 European and N. American Emissions

Circuit Description

The pressure control valves 3, 4, 5, and 6 are precision electronic pressure regulators that control the operation of the clutches, brakes, and 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 pressure control valves require a constant input pressure.

Conditions for Setting the DTC

    • Output voltage of the solenoid valve 4 is less than 2 volts.
    • No DTC P1862, P1863.
    • Immediately after the above condition occurs

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 ignition OFF/ON: 3rd gear by hydraulic control. Possible P, R, and N also possible.
    • Power supply cut off to the pressure control solenoid 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 P1861 sets, the possible cause of fault could be the pressure control valve 4.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select Actuating on the scan tool.
  4. Actuate pressure control valve 4 ON/OFF.

Does the valve change ON/OFF?

--

Go to Diagnostic Aids

Go to Step 3

3

  1. Turn the ignition OFF.
  2. Disconnect the transaxle wiring connector.
  3. Measure the resistance between terminals 5 and 7 of the transaxle wiring connector.

Is the resistance within the specified value?

TFT 25°C (77°F)

6 ohms

Go to Step 7

Go to Step 4

4

  1. Remove the oil pan.
  2. Disconnect the wiring connector of pressure control solenoid valve 4.
  3. Measure the resistance between terminal 2 of the solenoid valve 4 and ground.
  4. Measure the resistance between terminal 1 of the solenoid valve 4 and ground.

Is the resistance within the specified value?

Go to Step 6

Go to Step 5

5

Repair the internal line for valve 4 for a short to ground.

Is the repair complete?

--

System OK

--

6

Replace solenoid valve 4.

Is the replacement complete?

--

System OK

--

7

  1. Disconnect the transaxle wiring connector and transmission control module (TCM) connector.
  2. Measure the resistance between terminal 5 of the transaxle wiring connector and ground.
  3. Measure the resistance between terminal 7 of the transaxle wiring connector and ground.

Is the resistance within the specified value?

Go to Step 9

Go to Step 8

8

Repair the transaxle wiring harness for a short to ground.

Is the repair complete?

--

System OK

--

9

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the replacement complete?

--

Go to Step 10

--

10

  1. After the repair, use a scan tool Clear Info function and road tests the vehicle.
  2. Review the DTC Info.

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

--

Go to Step 2

System OK