Jetta L4-1781cc 1.8L SOHC (1987)
Oxygen Sensor: Testing and Inspection
Oxygen Sensor System (Digifant II)
DIGIFANT II
Oxygen Sensor System - Checking
Requirements
-
Engine oil temperature must be at least 80°C (176°F) and radiator cooling fan must come on at least once.
-
Idle speed, timing, and CO content OK.
-
The exhaust system between catalytic converter and cylinder head is not leaking
-
The voltage supply for oxygen sensor heater is OK.
-
The coolant temperature sensor and oxygen sensor connected.
-
All electrical consumers switched OFF and radiator cooling fan must not be running during checking or adjusting.
-
Remove the cap from the CO tap tube.
-
Connect EPA 105 CO tester (or EPA approved equivalent) to CO tap tube using only special tool 6006-0019 or equivalent (non-approved hoses
may dramatically alter the readings).
-
Start the engine and raise speed to a minimum of 2100 RPM four times, letting the throttle close each time.
-
This clears the fault memory in the E.C.U. and cancels the hot-start idle increase function.
-
Check CO and record reading.
-
Remove the oil fill cap from valve cover and observe CO reading.
-
CO content must drop briefly and then increase to original value.
Note: If the CO content does not drop, there is a vacuum leak in the system.
If CO content does return to original value:
-
Oxygen sensor system is OK and compensating properly.
-
Re-install oil filler cap.
If CO content does not return to original value:
-
Switch engine OFF and re-install oil filler cap.
-
Disconnect oxygen sensor at 3-way connector.