Check On-Board Diagnostic Unit

Check On-board Diagnostic Unit:





The diagnostic unit consists of two units connected together, A and B. Connect selector cable to output 1 on diagnostic unit B.

Check LED:





- Ignition on.
- Press button on diagnostic unit A. LED should come on when button is pressed.
- If not, go to "Check power supply".
- If LED comes on but no code appears, go to "Check diagnostic signal from control module"(below).

Check Power Supply:





- Ignition on.
- Remove connector from underside of diagnostic unit A. Connect a voltmeter between ground (GND) and connector A. Voltmeter should read battery voltage.
- If value OK, go to "Check GND point.
- It not, check fuse 33 and wires to it for breaks as in "Check cables". Checking Wires

Check GND Point:





- Ignition off.
- Remove connector from underside of diagnostic unit A. Connect an ohmmeter between GND and 8 on connector A. Ohmmeter reading should be about 0 ohms.
- If value is OK, test with new diagnostic unit.
- If not, check GND point and wires to it for breaks as in "Check cables". Checking Wires

Check Diagnostic Signal From Control Module:





- Ignition on.
- Remove selector cable from B1. Connect a voltmeter between GND and 1 on diagnostic unit B. Voltmeter reading should be approx. 10 V.
- It value is OK, replace diagnostic unit.
- If not, check wire between A:30 on control module and 1 on diagnostic unit B for breaks or GND shorts as in "Check cables". Checking Wires