ZF 4HP 16 - Automatic Transmission (Non-European Emissions)

DTC P0734 (Non-European Emissions)

Circuit Description

The transmission control module (TCM) uses transaxle input speed information and output speed sensor to control line pressure, torque converter clutch (TCC) apply and release, and transaxle shift patterns. This information is also used to calculate the appropriate operating gear ratios and the TCC slippage.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0734 Incorrect 4th Gear Ratio

Conditions for Setting the DTC

* Time since TCM reset is greater than 500 ms.
* Time since shift end is greater than 500 ms.
* Transmission oil temperature is greater than -10°C (14°F).
* System voltage is greater than 9 volts.
* No input speed error DTCs P0715, P0716, and P0717
* Output speed is greater than 256 RPM.
* Input speed is greater than 400 RPM.
* No gear shift active

Action Taken When the DTC Sets

* The hold lamp will blink.
* 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.
* High line pressure

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

* Inspect for intermittent input speed sensor or output speed sensor circuit problems.
* Inspect for possible incorrect calibration.