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Home >> Chevrolet >> 2007 >> Optra LT, Automatic >> Repair and Diagnosis (Single Page) >> Brakes >> Traction Control >> Antilock Brake System >> Diagnostic Information and Procedures >> DTC C0121 (North America) >> Diagnostic Aids

Diagnostic Aids

It is very important to perform a thorough inspection of the wiring and the connectors. Failure to do so may result in misdiagnosis, causing part replacement with reappearance of the malfunction.

Step Action Values Yes No
Schematic Reference:  Antilock Brake System Schematics  
Connector End View Reference:  Antilock Brake System Connector End Views  
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Use a scan tool to clear all diagnostic trouble codes (DTCs).
  2. Road test the vehicle.
Does DTC C0121 set again?		 - Go to Step 4  Go to Step 3 
3
  1. Inspect all system wiring harness connectors and terminals, especially the electronic brake control module (EBCM), for any problem that could cause an intermittent condition.
  2. Repair any intermittent problem found.
Did you complete the action?		 - Go to Step 11  -
4
  1. Disconnect the antilock brake system (ABS) harness connector J1 from the EBCM.
  2. Examine terminal 13 on the harness connector and the EBCM connector.
Is there damage or corrosion at terminal 13?		 - Go to Step 5  Go to Step 6 
5 Repair the terminal or the connector, or replace the ABS harness or ABS unit as required.
Did you complete the action?		 - Go to Step 11  -
6 Measure the resistance from terminal 13 of the harness connector J1 to a good chassis ground.
Is the resistance equal to the specified value?		 0 Ω Go to Step 7  Go to Step 8 
7 Replace the EBCM.
Did you complete the replacement?		 - Go to Step 11  -
8 Measure the resistance from terminal 13 of the harness connector J1 to the ground lug at G106.
Is the resistance equal to the specified value?		 0 Ω Go to Step 9  Go to Step 10 
9 Repair the chassis connection at the ground lug.
Did you complete the repair?		 - Go to Step 11  -
10 Repair the open or the high resistance in the ABS harness, or replace the harness as required.
Did you complete the action?		 - Go to Step 11  -
11
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?		 - Go to Step 2  System OK
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