If Main relay (Engine control relay) does not work normally, possible causes are abnormal IG key "ON" signal, ECM power, ECM ground and faulty ECM. If Main relay does not work normally, ECM is not operated. Therefore trouble shooting by using a scantool is impossible.
If IG key "ON" signal is input, Main relay is operated at the same time by ECM. If IG key "OFF" signal is input, injector working is stopped by ECM and Main relay is to be "OFF" after few seconds.
Diagnostic Procedure
IG key "ON" power inspection
1.
Inspect fuse blown related to ignition switch power.
Symptom
Inspection procedure
Case1
● Fuse is normal and IG power is supplied normally.
● Go to "Next step" as below.
Case2
● Fuse is blown.
● Repair short to ground in ignition power switch circuit.
2.
Check voltage between ignition power supply (IG switch signal) terminal of ECM harness connector and chassis ground.
☞ IG key "ON" : IG power is supplied (11.5V~13.0V)
☞ IG key "OFF" : IG power is NOT supplied (below 2.0V)
Symptom
Inspection procedure
Case1
● Ignition power supply (IG switch signal) is input normally according to IG key "ON", "OFF".
● Go to "Main relay circuit inspection"
Case2
● Ignition power supply (IG switch signal) is NOT supplied at IG KEY "ON".
● Repair open in ignition power supply (IG switch signal) circuit.
