Instructions concerning the HHT gas injection and ignition system (pressurized engine control)

 Troubleshooting with HHT

Diagnostic fault code memory: select current fault

If the current status changes, e.g. due to a loose connector, the change is indicated visually and acoustically so that troubleshooting can take place immediately with the HHT.

 Loose contacts

Loose contacts are stored if they occur a number of times within a certain time interval. Thus they can only occur as stored faults and never as current faults.

 Specified values

All the specified values for the actual values displayed in the HHT are given in the engine diagnosis manual.

 Actual value temperature coolant/intake air

If there is discontinuity or a short circuit there is immediate switch-over from the current actual value to a substitute value which lies very close to the actual value. This means that the fault is not clearly recognizable. Reading out of the fault is only possible over the diagnostic fault code memory.

 Actual value for the intake manifold pressure

There is immediate switch-over from the current actual value to a substitute value which lies very close to the actual value if the intake manifold pressure is missing at the control unit or there is a defect on the pressure sensor in the control unit. This means that the fault is not clearly recognizable. Reading out of the fault is only possible over the diagnostic fault code memory.

 Actual value for engine speed

Concerning engine speed, the specified value for idling speed calculated by the control unit is displayed on the left of the HHT display and the engine speed actual value is on the right. The two values should only deviate slightly.