Diagnostic Aids

Codes 1148, 1234 and 1259 are generated by ECU detecting a missing, erratic or improper signal from right front sensor circuit.

Code 1148 indicates erratic right front sensor information. This code only set at speeds greater than 12 MPH.

Code 1234 indicates erratic left front sensor information. This code only set at speeds greater than 12 MPH.

Code 1259 indicates left front sensor signal does not match right front and rear sensor signals.

Codes will not set with vehicle stationary.

The following conditions may be cause of problem:

• Shorted or open sensor.
• Shorted or open circuit between ECU and sensor.
• Defective trigger circuit in ECU.

1. Check Code
   
   Retrieve codes. If Code 1145 and any combination of Codes 1148, 1234 or 1259 are set, service Code 1145 and ignore all other codes. Go to step  6 . If any single code or combination of Codes 1148, 1234 or 1259 are set, go to next step.
2. Check Circuit Signal
   
   Scan tester capable of monitoring wheel speed must be used in this step. Test drive vehicle. Accelerate vehicle smoothly and gradually to 20 MPH. Hold speed for at least 15 seconds then decelerate. If right front speed signal remains at zero while left front and rear speed signals indicate acceleration above 4 MPH, go to step  4 . If all wheel speed signals indicate same speed, go to next step.
   NOTE: If a hard turn is made during test drive, some variation between all 3 sensors is expected. Rear speed signal should always fall between the left and right front speed signals.
3. Check Signal Mismatch
   
   Drive vehicle at various speeds. Using scan tester, monitor wheel speed signals. If right front speed signal consistently matches left front and rear axle speed signals, condition is intermittent. Go to step  11 . If right front speed signal is not consistent with left front or rear axle speed signals, damaged sensor ring or incorrect air gap exists, go to next step.
4. Check Sensor Ring
   
   Raise and support vehicle. Remove right front wheel and rotor. Rotate and inspect sensor ring for damaged or missing teeth. Replace sensor ring if damaged. Go to step  16 . If sensor ring is okay, go to next step.
5. Check Sensor Tightness
   
   Check right front speed sensor for looseness. Tighten sensor as necessary and go to step  16 . If sensor is tight, go to next step.
6. Check Sensor For Short
   
   Disconnect right front sensor connector. Measure resistance between a good known ground and both sensor terminals. If resistance is less than 100,000 ohms at either terminal, replace sensor and go to step  16 . If resistance is more than 100,000 ohms at both terminals, go to next step.
7. Check Sensor Output
   
   Turn ignition off. Disconnect ECU 40-pin connector to prevent erroneous codes from being stored. Disconnect right front sensor connector. Set Rotunda Meter (105-00053) or equivalent, to frequency counter (Hz) setting. Start engine and accelerate vehicle slowly up to 20 MPH. Measure frequency between 2 terminals of right front sensor. Change meter to A/C mV setting. Measure and record voltage output between 2 terminals of right front sensor. Ensure both measurements are recorded at same wheel speed. Determine sensor output in mV/Hz, by dividing A/C voltage reading by frequency reading. If sensor output is more than 13 mV/Hz, output indicates sensor signal are okay. Go to step  9 . If sensor output is less than specified, sensor output is insufficient. Go to next step.
8. Check Sensor Mounting
   
   Ensure sensor mounting surface is clean, and sensor is mounted correctly. Ensure sensor ring is mounted correctly. If sensor ring is not pressed on straight or axle end play is excessive, repair as necessary and go to step  17 . If sensor mounting surface is clean, sensor is mounted correctly and sensor ring is mounted correctly, replace sensor. Go to step  17 .
9. Check Circuit Output
   
   Turn ignition off. Disconnect ECU 40-pin connector. Install Breakout Box and adapter. Connect right front speed sensor connector. Set Rotunda Meter (105-00053) or equivalent, to frequency counter (Hz) setting. Start engine and accelerate vehicle slowly up to 20 MPH. Measure and record frequency between breakout box pins No. 8 and 34. Change meter to A/C mV setting. Measure and record voltage output between breakout box pins No. 8 and 34. Ensure both measurements are recorded at same wheel speed. Determine sensor output in mV/Hz, by dividing A/C voltage reading by frequency reading. If sensor output is more than 13 mV/Hz, output at ECU indicates sensor signal are okay. Replace ECU and go to step  16 . If sensor output is less than specified, sensor output at ECU is insufficient. Go to next step.
10. Check Wiring
    
    Disconnect right front sensor connector. Measure resistance between breakout box pins No. 8 and 34. If resistance is less than 100,000 ohms, Yellow/Black and Yellow/Red wires are shorted together. Repair as necessary and go to step  16 . If resistance is more than 100,000 ohms, repair short to ground in Yellow/Black or Yellow/Red wire. Go to step  16 .
11. Check Sensor Wiring
    
    Monitor resistance between sensor terminals. Wiggle brake hose and sensor wire harness along its entire length. If resistance changes, repair wire harness as necessary and go to step  16 . If resistance does not change, go to next step.
12. Check Sensor For Damage
    
    Remove right front speed sensor. Inspect plastic housing for stress, cracks or breaks. Inspect sensor connector cavity for evidence of water entry, pin corrosion or excessive debris. Replace sensor as necessary and go to step  16 . If water entry or pin damage is found, replace both halves of 2-pin connector assembly. Pack sensor connector cavity with dielectric grease. Go to step  16 .
13. Check Intermittent Sensor Open
    
    Disconnect right front sensor connector. Drive vehicle over rough road while monitoring resistance between sensor terminals. Test drive must be long enough to bring sensor to normal operating temperature. If resistance is less than 3000 ohms, sensor has intermittent malfunction. Replace sensor and go to step  16 . If resistance is more than 3000 ohms, go to next step.
14. Check Intermittent Sensor Short
    
    Drive vehicle over rough road while monitoring resistance between a good known ground and both sensor terminals. If resistance is less than 100,000 ohms at either terminal, replace sensor and go to step  16 . If resistance is more than 100,000 ohms at both terminals, sensor is okay. Go to next step.
15. Check Intermittent Wiring
    
    Turn ignition off. Disconnect ECU 40-pin connector. Install Breakout Box and adapter. Drive vehicle over rough road at various speeds while monitoring continuity between breakout box pins No. 1 and 8, No. 1 and 34, and No. 8 and 34. If continuity is indicated at any set of pins, repair source of malfunction in Yellow/Black and Yellow/Red wire. If continuity is not indicated at any set of pins, replace sensor. Go to next step.
16. Verify Repair
    
    Remove breakout box and adapter. Connect all components. Clear all codes and cycle ignition key. Drive vehicle and complete at least one hard left and right turn. Travel over a rough road at steady speed. Perform one hard and one normal acceleration from a stop. At completion of test drive, retrieve codes. If SYSTEM PASS is set, condition has been repaired and test is complete. If original code is set, cause of condition may be wiring related. Go to step  15 . If a different code is set, go to appropriate TEST under TESTS  .
17. Verify Signal
    
    Scan tester which is capable of monitoring wheel speed must be used in this step. Test drive vehicle. Accelerate vehicle smoothly and gradually to 20 MPH. Hold speed for at least 15 seconds then decelerate. If right front speed signal remains at zero while left front and rear speed signals indicate acceleration above 4 MPH, go to step  8 . If all wheel speed signals indicate same speed, condition has been repaired and test is complete.