Entering Self Diagnostics

A technician requests the ECU to flash the "Antilock" light ON and OFF to indicate the number of its stored code by doing the following:

^ Turning the ignition switch to the "run" position
^ Installing a jumper wire between ALDL terminals H to A (or chassis ground)
^ Waiting two to three seconds

ALDL Connector:

Antilock Light Code Flashing:

^ Watching the "Antilock" light flash ON and OFF in a manner similar to the ECM for the fuel/transmissions system.
With the brake pedal released, the light may flash a Code 12 or Code 14 three times before it flashes its stored codes, (refer to code description). It will then flash stored codes three times each in a continuous series. The light may flash a Code 13 or Code 15, if the brake pedal is pressed (or the switch circuit is open), followed by the code display.


CODE DESCRIPTION

12 SYSTEM NORMAL (2WD)
13 SYSTEM NORMAL - BRAKE APPLIED (2WD)
14 SYSTEM NORMAL (4WD/AWD)
15 SYSTEM NORMAL - BRAKE APPLIED (4WD/AWD)

21 RF WHEEL SPEED SENSOR HAS INCORRECT RESISTANCE
22 RF WHEEL SPEED SENSOR HAS INCORRECT VOLTAGE OUTPUT
23 RF WHEEL SPEED SENSOR HAS ERRATIC VOLTAGE OUTPUT

25 LF WHEEL SPEED SENSOR HAS INCORRECT RESISTANCE
26 LF WHEEL SPEED SENSOR HAS INCORRECT VOLTAGE OUTPUT
27 LF WHEEL SPEED SENSOR HAS ERRATIC VOLTAGE OUTPUT

28 ERRATIC SENSOR (1 TO 2 "DROP OUTS")
29 SIMULTANEOUS "DROP OUT" OF ALL FOUR SENSORS

31 RR WHEEL SPEED SENSOR HAS INCORRECT RESISTANCE
32 RR WHEEL SPEED SENSOR HAS INCORRECT VOLTAGE OUTPUT
33 RR WHEEL SPEED SENSOR HAS ERRATIC VOLTAGE OUTPUT

35 LR WHEEL SPEED SENSOR HAS INCORRECT RESISTANCE
36 LR WHEEL SPEED SENSOR HAS INCORRECT VOLTAGE OUTPUT
37 LR WHEEL SPEED SENSOR HAS ERRATIC VOLTAGE OUTPUT

38 WHEEL SPEED SENSOR ERROR (2:1 SIGNAL RATIO ABOVE 12 MPH)

41 - 66 4WAL CONTROL UNIT
71 - 74 4WAL CONTROL UNIT
67 OPEN MOTOR CIRCUIT OR SHORTED EHCU OUTPUT
68 LOCKED MOTOR OR SHORTED MOTOR CIRCUIT

81 BRAKE SWITCH CIRCUIT SHORTED OR OPEN

85 OPEN ANTILOCK WARNING LAMP
86 SHORTED ANTILOCK WARNING LAMP
88 SHORTED BRAKE WARNING LAMP

NOTE: SIMULTANEOUS CODES 68, 43, 44, 47, 48, 53 AND 54 INDICATE POWER OR GROUND CIRCUIT FAULT