Code 21: Front Wheel Speed Sensor Open Circuit
NOTE:
Code 21 is output if speed signal of front wheel has differed from rear wheel by 5 MPH or more, due to open circuit.
- Retrieve electronically controlled automatic transmission trouble codes. See RETRIEVING CODES under SELF-DIAGNOSTIC SYSTEM. If code 32 is output, see the TRANSMISSION SERVICING article. If code 32 is not output, turn ignition off.
- Disconnect TCL module harness connector. See Figure . Disconnect transmission control module harness connector. See Fig 1 . Using ohmmeter, check continuity between TCL module harness connector terminal No. 55 and transmission control module harness connector terminal No. 10. See Figure and Fig 2 .
- If continuity does not exist, inspect and repair circuit as needed. See appropriate wiring diagram in WIRING DIAGRAMS. If continuity exists, check for continuity between circuit and vehicle ground. If continuity exists, inspect and repair circuit for short to ground. If continuity does not exist, replace automatic transmission control unit. See AUTOMATIC TRANSMISSION CONTROL UNIT under REMOVAL & INSTALLATION.