Note Regarding Diagnostic Trouble Code (DTC) Readout

Note regarding diagnostic trouble code (DTC) readout:
- DTC memory: Fault display
Actual faults: are on a grey background
Stored faults: are on a light background

The signal plausibility is checked on all input and output connections during operation.

All malfunctions which occur are stored in the diagnostic trouble code memory of the IF control module (N3/7).

The DTC memory remains active even if the ignition is turned "OFF" or the vehicle's battery is disconnected.

With emission related faults the CHECK ENGINE MIL (A1e26) lights up and/or the multifunction indicator displays:
CHECK ENGINE
ENGINE ELECTRONICS.

The faults are identified with an OBD failure code: See Trouble Code Description. Diagnostic Trouble Code Descriptions

Such faults are for example:
- EGR lifting sender (B28/3)
- EGR valve vacuum transducer (Y31/l)
- Pressure control flap vacuum transducer (Y31/2)

Fault freeze frame data
Additionally, ambient conditions present at the time the fault occurs, can be displayed with the HHT. Only those freeze frame data are stored which were present when the fault first occurred. The freeze frame data may be indicated on several screen displays (up to 8 screen displays). The last two screen displays are for development purposes only.





Substitution for missing signals.
The IFI control module (N3/7) replaces missing input signals with substitute values based on other signals available in order to maintain system function.
The substitute values may result in:
- Performance reduction/reduction of maximum engine rpm.
- Switching off anti-vibration control.
- EGR system malfunction.
- Cruise control malfunction.
- Intake MAP control malfunction.

Operating Cycle (USA) version only
One operating cycle is reached if:
- Engine coolant temperature > 60° C
- Engine rpm for 5 seconds at 2500 rpm
- Ignition OFF for 5 seconds
- Engine rpm for 5 seconds at 2500 rpm
- Ignition OFF for 5 seconds
- Engine rpm for 5 seconds at 2500 rpm

See HHT Menu 3/8 Memory storage enablement OBD II.

Prerequisite for DTC memory readout
1. Fuse on relay module (K40) in order.
2. Connect HHT to data link connector (X11/4, 38-pole) according to connection diagram. Connection Diagrams
Yellow wire to socket 4.