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OBD I Trouble Codes

Decoding your VIN
OBD I Fault Code Detail
Code 27 / 28
Gear Switches Circuits
The gear switches are located inside the transaxle.  They are pressure switches, normally closed.  The ECM supplies 12 volts through each selected circuit to the switch.  In any condition other than the specific gear application, the signal line monitors low voltage, low potential.  As road speed increases, hydraulic presure applies the specific gear clutches and the gear switch opens.  At this time, the ECM monitors a high, 12 volt potential, and interprets this to indicate that gear is applied.  The ECM uses the gear signals to control fuel delivery and TCC.

Code 27 will set if:
-  Second gear circuit indicates ground or closed switch for 10 seconds when vehicle is in second gear operation.
-  Second gear curcuit indicates an open (drive) when the engine is first started.

Code 28 will set if:
-  Third gear circuit indicates ground or closed switch for 10 seconds when vehicle is in third gear operation
-  Third gear circuit indicates an open (drive) when the engine is first started.
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