Hey there I have a 2001 jeep grand Cherokee 4.7L the #8 individual ignition coil burns up with in 2 minutes. I did some testing and found that it is receiving full ground contact from the pcm/ecm even with...
The COP (coil on plug)
ignition system is what is used on most modern engines. There is an
individual coil for each cylinder that is controlled by the PCM
(powertrain control module). It eliminates the need for spark plug wires
by putting the coil right above the sparkplug. Two wires are dedicated
to each coil. One is a battery feed usually from the power distribution
center. The other wire is the coil driver circuit from the PCM. The PCM
grounds/ungrounds this circuit to activate or deactivate the coil. The
coil driver circuit is monitored by the PCM for faults
If an open or a short is detected in the driver circuit for coil #8, a
P0358 may set. Also, depending on the vehicle, the PCM may also shut
down the fuel injector to the cylinder also.
Symptoms
Symptoms of a P0358 DTC may include:
MIL (Malfunction indicator lamp) illumination
Engine misfire may be present or intermittent
Causes
Potential causes of a P0358 code include:
Short to voltage or ground on COP driver circuit
Open on COP driver circuit
Loose connection at coil or broken connector locks
Bad Coil (COP)
Faulty Powertrain Control Module
Possible Solutions
Is the engine misfiring presently? If not, the problem is likely
intermittent. Try wiggle testing the wiring at the #8 coil and along the
wiring harness to the PCM. If manipulating the wiring causes the
misfire to surface, repair the wiring problem. Check for poor connection
at the coil connector. Verify the harness isn't misrouted or chafing on
anything. Repair as necessary
If the engine is misfiring presently, stop the engine and disconnect the
#8 coil wiring connector. Then start the engine and check for a driver
signal to the #8 coil. Using a scope will give you a visual pattern to
observe, but since most people don't have access to one there's an
easier way. Use a Voltmeter in AC Hertz scale and see if there's a Hz
reading of between 5 and 20 or so that indicates the driver is working.
If there is a Hertz signal, then replace the #8 ignition coil. It's
likely bad. If you don't detect any frequency signal from the PCM on the
ignition coil driver circuit indicating the PCM is
grounding/ungrounding the circuit (or there is no visible pattern on the
scope if you have one) then leave the coil disconnected and check for
DC voltage on the driver circuit at the ignition coil connector. If
there is any significant voltage on that wire then there is a short to
voltage somewhere. Find the short and repair it.
If there is no voltage on the driver circuit, then turn the ignition
off. Disconnect the PCM connector and check the continuity of the driver
between the PCM and the coil. If there is no continuity repair the open
or short to ground in the circuit. If continuity is present, then check
for resistance between ground and the ignition coil connector. There
should be infinite resistance. If there isn't, repair the short to
ground in the coil driver circuit
NOTE: If the ignition coil driver signal wire is not open or shorted to
voltage or ground and there is no trigger signal to the coil then
suspect a faulty PCM coil driver. Also keep in mind that if the PCM
driver is at fault, there may be a wiring problem that caused the PCM
failure. It's a good idea to do the above check after PCM replacement to
verify there won't be a repeat failure. If you find that the engine
isn't misfiring, the coil is being triggered properly but P0358 is
continually being reset, there is the possibility that the PCM coil
monitoring system may be faulty.
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