Engine Speed and Throttle Monitoring

AUTOMATIC TRANSMISSION – ZF 5HP24

DESCRIPTION AND OPERATION 44-2-51

Transmission Fault Status
If the EAT ECU detects a fault with the transmission system, it will enter a default mode to prevent further damage to 
the transmission and allow the vehicle to be driven.

When a fault is detected a CAN message is sent from the EAT ECU and is received by the instrument pack. The 
instrument pack illuminates the MIL and displays 'TRANS. FAILSAFE' in the message centre.

Some transmission faults may not illuminate the MIL or display a fault message, but the driver may notice a reduction 
in shift quality.

Engine Speed and Throttle Monitoring
The ECM constantly supplies the EAT ECU with information on engine speed and throttle angle through messages 
on the CAN. The EAT ECU uses this information to calculate the correct and appropriate timing of shift changes.

If the messages are not received by the ECM, the EAT ECU will implement a back-up strategy to protect the 
transmission from damage and allow the vehicle to be driven.

In the event of an engine speed signal failure, any of the following symptoms may be observed:

l

Decrease in fuel economy

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Increase in engine emissions.

In the event of a throttle position signal failure, any of the following symptoms may be observed:

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Harsh shift changes

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No kickdown

l

Torque reduction request inhibited.