Fault Code 21

Synopsis

Description: Oxygen sensor signal stays in neutral region too long
Power loss light: Off
Limp-in mode: Engine allowed to run rich, but prevented from running lean

Possible Causes

Bad connection or wiring - Check the wiring and connections between the sensor and the logic module (or SMEC). Clean and regrease any corroded connectors with dielectric grease and repair any shorts. Look for melted wire insulation near the exhaust manifold. An open connection will cause this fault code.

Bad oxygen sensor - Replace the sensor which is located on the turbo housing near the down pipe (for turbo) or on the down pipe near the exhaust manifold.

Diagnostic Method

Trigger Parameters

- In closed-loop for 718 seconds (11 minutes, 58 seconds)
- Sensor output stays in the neutral region for more than 21 seconds

Results If Component Fails

A fault code 21 is stored. The circuit stays in closed-loop and the logic module will still monitor the oxygen sensor signal and allow the engine to run rich, but prevent it from running lean.

Return to the Fault Codes Page

This page is maintained by Russell W. Knize and was last updated 08/28/98. Comments? Questions? Send email.