Cherokee 4WD L6-242 4.0L VIN S MFI (1992)
Oxygen Sensor: Testing and Inspection
Engine Controller Response Test
ENGINE CONTROLLER RESPONSE TEST
NOTE: A four gas analyzer will be needed to perform this test.
NOTE: This test should be performed only after sensor functional test, and sensor heating element tests are passed.
NOTE: When performing this test it is important that no part of your body contact the vehicle body, as inaccurate test results may result.
CAUTION: NEVER apply voltage directly to any computer sensor wire.
1.
Make sure the vehicle is at normal operating temperature. Run the engine at 2500 rpm for 3 minutes with the transmission in PARK (A/T) or
NEUTRAL (M/T).
2.
With engine OFF, disconnect oxygen sensor connector and connect a jumper lead to the computers oxygen sensor return wire, terminal 2 of the
electrical connector.
3.
Start engine and run at 2500 rpm for 1 minute with the transmission in PARK (A/T) or NEUTRAL (M/T).
4.
Let engine idle.
5.
Simulate a lean command (rich condition), by touching one hand to jumper wire and other hand to battery negative, for 10 to 20 seconds. HC and
O2 readings should begin to increase.
6.
Simulate a rich command (lean condition), by touching one hand to jumper wire and other hand to battery positive, for 10 to 20 seconds. HC and
O2 readings should begin to decrease, and CO should begin to increase.
7.
If computer system fails to respond to these artificial commands, further testing of the oxygen sensor circuit and/or computerized engine control
system will be necessary.
