Fuel Consumption Signal

Checking Fuel consumption signal

NOTES:
- The consumption signal is internally calculated by the ECM using "injection time."
- The consumption signal is routed to both the trip computer and the Transmission Control Module (TCM).
- The consumption signal is monitored by the TCM.

- Carry out the following check only if DTC memory contains a stored DTC for the TCM related to the consumption signal, or a missing or false consumption signal, determined during the trip computer check.

- Remove instrument cluster or TCM.

- Connect VAG 1598 test box to instrument cluster harness connector (I/P insert not connected) or to TCM harness connector (TCM not connected).

- Switch Fluke 83 multimeter to voltage measurement range and connect between signal wire (trip computer 20-pin connector) and Ground (GND), using wiring diagram.

- Start engine and let idle.
Specified value: approx. 0.3 to 0.6 volts, corresponding to engine speed (RPM)
- Vary engine speed continuously from 1000 to 4000 RPM.
Specified value: approx. 0.3 to 0.6 volts, corresponding to engine speed (RPM)

If the specified value is not obtained, even though the trip computer shows no consumption value or there is a stored malfunction in the TCM:
- Stop engine (switch ignition off).
- Replace trip computer and/or TCM as required. If the specified value is not obtained:
- Check wiring between ECM terminal C12 and black 20-pin trip computer connector, using wiring diagram.

If wiring OK and the specified value is not obtained:
- Replace ECM.