Fault Code 21
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
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
- 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.
This page is maintained by Russell W. Knize and was last updated 08/28/98.
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Copyright © 1996-2003 Russ W. Knize