Oxygen Sensor System - Checking
85VW1Applies To
GOLF
(U.S.. models with manual trans. only)
1985
Group 26
Subject
CIS With OXS System
Part Identifier N/A
Key Points
Oxygen sensor system, checking
B
Number
85-01
April 17, 1985
Oxygen sensor system, checking
Work sequence
- connect tester VW 1367 as follows
- connect + lead to positive battery terminal
- connect - lead to negative battery terminal
- connect dwell lead to OXS test connection (blue/white and brown wires) using harness adaptor US 1112
- press % button on testor VW 1367
- disconnect ignition coil high tension wire from ignition distributor cap and connect to ground with jumper wire
- remove fuel pump relay from fuse/relay panel
- switch US 4480/3 OFF
- connect US 4480/3 in place of fuel pump relay in fuse/relay panel
- continue with test procedures
Frequency valve, checking
- switch US 4480/3 ON
^ frequency valve must make buzzing noise
If YES
- frequency valve OK, go to next test
If NO
- frequency valve NOT OK, continue as follows
- unplug frequency valve connector
- check terminals of connector and frequency valve for correct position or damage
If terminals OK
- connect ohmmeter across terminals of frequency valve
^ must read 2-3 Ohms
If ohm reading NOT OK
- replace frequency valve and recheck
If ohm reading OK
- check for voltage across terminals of frequency valve connector with test light
^ test light must go ON
If light goes ON
- replace frequency valve and recheck
If light DOES NOT go on
- check for open circuit in wiring between frequency valve connector, oxygen sensor relay and control unit (refer to current flow diagram)
If circuits OK
- replace oxygen sensor relay
If light still DOES NOT go on
- replace OXS control unit and recheck system
OXS control unit, checking
Cold enrichment
- switch US 4480/3 ON
- unplug OXS thermoswitch connectors (arrow)
- check reading displayed on VW 1367
^ must be steady 50% +/- 2% (45 +/- 2~ dwell)
- bridge terminals of OXS thermoswitch connectors (arrows)
- check reading displayed on VW 1367
^ must be steady 80% +/- 2% (72 +/- 2~ dwell)
If either reading NOT OK
- check for open circuit in wiring between connector and OXS control unit
If wiring OK
- replace OXS control unit
- remove bridge at connectors
- check continuity of OXS thermoswitch with ohmmeter
^ above 30~C (86~F) = infinite Ohms
^ below 20~C (68~F) = 0 Ohms
If readings NOT OK
- replace thermoswitch
Rich-limit testing (tester reading increases)
^ US 4480/3 switched ON
^ OXS thermoswitch connector unplugged (if engine cold)
- unplug oxygen sensor at connection and ground green wire
- check reading displayed on VW 1367
^ must be at least 87% (78~ dwell)
If reading NOT OK
- check for open circuit in wiring to OXS control unit
If wiring OK
- replace OXS control unit
If reading OK
- continue with lean-limit testing
Oxygen sensor, checking
^ switch of US 4480/3 ON
^ thermoswitch connector removed
- disconnect crankcase ventilation hoses 2 and 3 and vent to atmosphere
- reconnect wire to oxygen sensor
- reconnect coil wire into distributor cap
- start engine and hold at 2500 rpm for more than two minutes
Note
After engine running more than two minutes, exhaust gas will warm sensor and it will start to work (reading fluctuates)
- check reading on tester at idle speed (idle speed must be within specifications)
^ reading on tester must fluctuate
If reading NOT OK (constant at 13% or 87% [12~ or 78~ dwell])
- CO may be out of specs. See Repair Group 25, Product Circular 85-02
If reading is a steady 50% (45~ dwell) or constant at specification limits and OXS control unit OK
- replace oxygen sensor
- reconnect thermoswitch connector
- reinstall crankcase breather hoses
- remove US 4480/3