Maintenance Required Lamp/Indicator: Description and Operation
As of 1986-1988 USA Models and Federal Models as of 1991The failure of an oxygen sensor is indicated by the "O2 sensor" warning lamp (A1e10) in the instrument cluster (A1) coming on (1988 and as of 1991 Federal: inscription "CHECK ENGINE" (A1e26)).
The warning lamp is actuated by the KE control unit, contact 15 (as of 1991 Federal: KE control unit contact 23).
See Computers and Control Systems for Diagnosis and reset procedure.
"CHECK ENGINE" Warning Lamp - USA 1988/As of 1991 California Version
The "CHECK ENGINE" warning lamp (A1e26) lights up if an exhaust system component fails. The warning lamp is actuated by the KE control unit, contact 23.
See Computers and Control Systems for Diagnosis and reset procedure.
O2 Sensor Replacement Indicator (California Only) - As of 1992
In addition to the "CHECK ENGINE" warning lamp, an O2 replacement indicator lamp (A1e33) is installed in the instrument cluster.
Upon reaching 60,000 miles ± 250 miles (i.e. every 60,000 miles), illumination of the lamp indicates that the O2 sensor must be replaced. For instructions on how to turn off the lamp, see Service and Repair. Service and Repair
Activation of the lamp is via the control unit N44/1, which is located in the passenger footwell.
The Hall-effect sensor output on the speedometer provides information on miles driven. The number of impulses per mile is determined by mutiplying a fixed number by the number of impulses from the Hall-effect sensor. The resulting distance is stored in the control unit.
The warning lamp comes on with the ignition/starter switch in position "2" and goes out again with the engine running (circuit 61 recognition).
O2 Sensor Replacement Control Unit:
A test mode is initiated if the button (arrow) is pressed for longer than 5 seconds with the ignition/starter switch in position "2". The test mode start is indicated by the O2 sensor warning lamp switching off.
- After a pause of 5 seconds, the recorded mileage is indicated by a blink impulse. The light blinks once for every 10,000 miles recorded.
- After a 2 second pause, the lamp blinks once for every additional 1,000 miles recorded.
- After a further 2 second pause, the lamp blinks once for every additional 100 miles recorded.
- If the recorded mileage is 0 (zero), this is indicated by the lamp not blinking.
- After a further 5 second pause, the operation of the Hall-effect sensor is tested. After the required 5 second pause the O2 sensor warning lamp should blink continuously if the vehicle is driven on the road or dynamometer.
The test mode can only be interrupted by switching the ignition off.