| Test | TECH 1 | Notes | Nominal Values | Pin | Possible |
|---|---|---|---|---|---|
| Step | Display | Trouble | |||
| No. | Codes | ||||
| 28 | O2 SENSOR LOOP | Engine at idle speed, | CLOSED | - | MY '89: |
| operating temperature | 13, 44, 45 | ||||
| 29 | O2 SENSOR | Engine at idle speed, | Voltage change | 28/10 | MY '90: |
| operating temperature | between 40 and 1000 mV | 13, 38, 39 |
Trouble-shooting: Nominal Value: Cause of Fault:
(If nominal value is not attained)
· Ignition ON
· Separate oxygen sensor 0.4 to 0.5 V · Lead interruption from
wiring harness plug - Control unit Ter. 28 to oxygen
sensor (signal lead)
Measure voltage between oxygen sensor - Control unit Ter. 10 to ground
signal lead Ter. C and ground Ter. A - Oxygen sensor to ground
at control unit
· Short circuit of
oxygen sensor signal lead
- To ground (display 0 V)
- To voltage (display > 1.0 V)
· Connect Adapter Cable KM-609 and Voltage change · If control loop closes only very slowly:
reconnect control unit and between 0.1 and 0.9 V - Oxygen sensor heating defective
oxygen sensor - Lead interruption from K 68 Ter. 87b
to oxygen sensor
Engine running at 1200 to 1600 rpm - Lead interruption from oxygen sensor
with coolant temperature ³85 °C/185 °F (heating sensor) to ground
Measure oxygen sensor · Oxygen sensor defective
voltage with engine running
· Mixture always too rich (s. test step 30)
· Mixture always too lean (s. test step 30)
· Control unit defective