6-Pin
Power:
Verify battery power and ground at the diagnostic port. Check for battery voltage (minimum 10V) between Pin E (Ground) and Pin C (Power). If no voltage or low voltage is present, check Pins E and C individually to identify whether there is a loss of ground or voltage.
Communication:
– Pin E (Ground)
– Pin A (HI)
– Pin B (LO)
With the switch in the “ON” position, measure the voltage between Pins E and A. The voltage should be between 3.00V and 4.50V, with readings fluctuating in the thousandths place, indicating the data bus is functioning correctly. Next, check the low voltage circuit of the data link between Pins E and B. The voltage here should be between 0.500V and 1.500V, also fluctuating in the thousandths position.
If the voltage readings on all wires are correct, it’s likely that the module you’re trying to communicate with is either not powered up or has an internal fault.
No Communication:
If one or both wires show zero voltage, check for a shorted module or damaged wiring.
Another approach is to disconnect each ECM module one by one and re-test after each disconnection. This can help isolate the faulty module, directing you to a more specific system for troubleshooting.
Additionally, check for a short to ground in the wiring on both Pins A and B. A short to ground on either wire could disrupt the entire data bus. Unplug all modules and check the resistance between Pin A and Pin E, and between Pin B and Pin E. Resistance should read as open (OL) in both cases.
TROUBLESHOOTING SHACK 