ZF 4HP 16 - Automatic Transmission

DTC P0727

Circuit Description

The transmission control module (TCM) is an electronic device which monitors inputs to control various transaxle functions including shift quality and transaxle sensors, switches, and components to process for use within the control program. Based on this input information, the TCM controls various transaxle output functions and devices.

DTCs P0725, P0726 and P0727 are related to the same circuit. These DTCs will not illuminate the HOLD or malfunction indicator lamp (MIL), however, the DTC will be stored in memory.

Information transmits between the TCM and engine control module (ECM) through the CAN line. Information is as follows :

* Engine malfunction signal
* Engine speed
* Engine output torque reduction signal
* Engine coolant temperature

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0727 Engine Speed No Signal

Conditions for Setting the DTC

* When turbine speed is more than 1,500 RPM, engine speed is less than 400 RPM.
* System voltage is too high or too low.
* CAN transmitting wiring harness shorted or open
* The TCM or ECM is defective.
* Immediately after the above condition occurs

Action Taken When the DTC Sets

* No lamp control
* 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.
* Open lock up clutch

Conditions for Clearing the MIL/DTC

* A history DTC will clear after 40 consecutive warm up cycles without a fault.
* Using a scan tool can clear history DTCs.