ZF 4HP 16 - Automatic Transmission (European and N. American Emissions)

DTC P1840 (European and N. American Emissions)

Circuit Description

The pressure control valves (PCS) 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 the electrical pressure regulating valves are supplied. As a result, smaller solenoid valves may be used. The PCS requires a constant input pressure.

Conditions for Setting the DTC

* Output voltage of the PCS 3 (at ON) is 12 volts.
* No DTC P1839, P1841.
* Immediately after the above condition occurs

Action Taken When the DTC Sets

* The malfunction indicator lamp (MIL) will illuminate.
* The 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 also possible.
* Power supply 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 P1840 sets, the possible cause of the fault could be the PCS 3 valve.