Diagnose and fix Hyundai Accent No Start
If you encounter a Hyundai Accent No Start condition on a late model vehicle, you may be looking at a bum ignition coil. BUT, if you just replace the coil and don’t finish the diagnostic work, you might be replacing the coil again and again.
Let’s define a no start condition
In this case we’re talking about an engine that cranks when you turn the key but won’t fire up like this:
Hyundai Accent burned ignition coils
Shops are reporting a high incidence of burned ignition coils that cause a Hyundai Accent no start condition. The symptoms are long cranking with either no start or a start with an extremely rough idle. What’s going on here is that and ignition coil has burned up from being ground full time. An ignition coil receives power power full time from the ignition switch. But it receives ground from the ECM only when it’s time to fire the spark plug. If the ground is on full time, the coil with overhead and self destruct.
What causes a burned ignition coil?
Two things can cause a coil to burn up; a short to ground somewhere in the wiring harness or a bad transistor “driver” in the ECM that fails in a short to ground mode, keeping power flowing through the ignition coil full time.
What causes an ECM driver to fail?
Two things can cause an ECM driver to fail; first, running your spark plugs too long can wear the electrode gap so large that the spark can’t jump the gap. That 50-80,000 volts has to go somewhere. So, if it can’t jump the gap, it looks for ground somewhere else. The voltage spike can fire right through the ignition coil to ground or it can burn out the transistor driver in the ECM. Or, it can degrade the primary windings in the coil, causing the coil to short out, which can also burn out the driver in the ECM.
How to test the ECM for a bad driver
See the schematic below. You see that the power flows to the ignition coil from the ignition switch. You want to do a voltage drop test on the two wires to the ignition coil while the coil is powered. If the driver in the ECM is good and the wiring harness is good, the ignition coil won’t have ground and you should see battery voltage on your meter. However, if you see a large voltage drop, around 0.30 volts, you’ve got a problem. You could have a wiring harness issue that’s shorting the ground wire to ground before the ECM, or a bad driver in the ECM. To check the wiring harness condition, disconnect the ignition coil connector at the ECM to isolate it from the ECM module. Redo the test. You should see battery voltage. If not, you’ve got a short to ground somewhere in the harness itself. Repair that and retest.
Replace the ECM
Do NOT buy a used ECM from the junkyard. Trust me on this. You’ll overpay and it probably won’t work. Get a rebuilt unit that’s fully programmed to your vehicle. Contact your auto parts store or do an online search for ECM rebuilders.
Prevent future ECM failures
ECM’s don’t fail by themselves very often. If a driver fails, it’s usually because you’ve neglected normal maintenance and tried to get too many miles out of your spark plugs. So replace spark plugs and coils BEFORE installing a rebuilt ECM, or you’ll just blow the new unit.
©, 2019 Rick Muscoplat
Posted on by Rick Muscoplat
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