What this code means
P0354 may indicate the PCM is detecting a possible problem in the ignition coil 4 primary or control circuit.
What the vehicle may do
- The MIL may be on.
- The engine may run rough or misfire.
- The vehicle may have reduced power or drivability complaints.
- In some cases, symptoms can be intermittent.
Possible fault areas
- Possible ignition coil power feed issue.
- Possible ignition coil 4 control circuit issue.
- Possible ignition coil or spark plug condition.
- Possible connector, terminal, or harness concern.
- Possible PCM coil driver concern after circuit checks support that direction.
Diagnostic path
Open on what P0354 is telling us
On this Ram 2500HD with the 6.4 HEMI gas engine, P0354 means the PCM may be seeing a problem on the ignition coil 4 primary circuit. In plain terms, coil 4 may not be getting the right feed or control, and the truck can show up with a misfire feel, rough running, reduced power, or just the MIL on. The broad areas to keep in mind are the fused ASD relay output feed, the coil 4 control circuit, the coil and spark plug condition, connector and terminal issues, and, later in the path, a possible PCM coil driver concern. This monitor runs continuously with the ignition on, and the code sets when the PCM sees the Ignition Coil 4 Signal circuit current less than, or equal to, 0.0 amps for at least 1.2 seconds.
Start by confirming the fault
Start with the basic system checks before chasing the circuit. Read and record DTCs from all ECUs, save the scan report and related data, then erase the codes. Turn the ignition off for a minimum of 10.0 seconds, turn it back on, and reproduce the operating conditions using the recorded data. Then read codes again. If P0354 does not return, treat it as an intermittent condition. If it does return, continue the circuit diagnosis.
Check for ASD-related code direction first
Before going deeper into coil 4, look back at the recorded codes. If any ASD-related DTCs are present, handle those applicable diagnostics first, because the coil feed depends on that relay output. If there are no ASD-related codes, move on to load testing the coil power supply.
Load test the coil 4 power feed
The ignition coil primary winding is supplied 12 volts from the fused ASD relay output circuit. Disconnect the Ignition Coil 4 connector and load test the power supply circuit at that connector to battery ground or chassis ground. Make sure the circuit is actually powered on for the test. The load test bulb should be illuminated and bright, and you should compare that brightness against a direct battery connection. If the bulb is not bright, repair the power supply circuit for an open or high resistance, then verify the repair and confirm the code stays gone. If the bulb is bright, continue to the control circuit test. If a test light is being used as the load tool, make sure it can actually load the circuit. A high impedance light that draws less than 0.1 amps is not reliable for this load test; the tool should draw more than approximately 0.75 amps. You can also use a voltage drop check across the 3156 bulb to be more certain the circuit is good.
Look at coil 4 control while cranking
Next, check the Ignition Coil 4 control circuit operation. Use a 12-volt test light connected to a 12.0 volt source, and probe the Coil 4 Control circuit at the ignition coil connector. Crank the engine for 5.0 seconds while watching the test light. Stay clear of the fan, pulleys, belts, and loose clothing any time the engine is cranking or running. If the test light blinks brightly, the control circuit is being pulsed, so continue to the spark plug inspection. If the light stays on constantly, the path goes toward checking the control circuit for a short to ground. If the light stays off constantly, the path goes toward checking the control circuit for an open or high resistance.
If the control signal blinks, inspect the spark plug
When the coil control signal is blinking correctly, turn the ignition off and remove the spark plug for that cylinder. Inspect it for cracks, carbon tracking, foreign material, gap size out of specification, and a loose or broken electrode. If one of those conditions is present, replace the spark plug, then verify the repair and confirm the code stays gone. If carbon tracking is found, also inspect the ignition coil boot for damage and replace it if necessary. If none of those spark plug conditions are present, replace the ignition coil and spark plug, then verify the repair and confirm the code stays gone.
If the control light stayed on, check for short to ground
If the test light stayed on constantly during the control circuit check, isolate the Ignition Coil 4 control circuit and check it for a short to ground. Turn the ignition off, disconnect the Ignition Coil 4 connector, disconnect the PCM connector, and check continuity between ground and the control circuit at the Ignition Coil 4 connector. If there is continuity to ground, repair the control circuit for a short to ground, then verify the repair and confirm the code stays gone. If there is no continuity, continue to the coil swap check before condemning the driver.
If the control light stayed off, check for open or high resistance
If the test light stayed off constantly during cranking, isolate the control circuit and check for an open or high resistance. Turn the ignition off, disconnect the Ignition Coil 4 connector, disconnect the PCM connector, and install the GPEC Diagnostic 10436 adapter at the appropriate PCM harness connector. Do not probe the PCM harness connectors directly, because that can damage the terminals and create a poor terminal-to-pin connection. Measure resistance in the control circuit between the Ignition Coil 4 connector and the PCM connector. The resistance should be below 3.0 Ohms. Also remember the GPEC Diagnostic Adapter can add up to 1.5 Ohms of resistance to the circuit. If resistance is not below 3.0 Ohms, repair the control circuit for an open or high resistance, then verify the repair and confirm the code stays gone. If it is below 3.0 Ohms, continue to the next step.
Check whether the coil is damaging the driver
Before replacing a PCM, determine whether the ignition coil itself may have caused a PCM coil driver failure. An internally shorted or damaged secondary coil circuit may be the reason the driver failed, so do not replace the PCM without first checking this. Remove the ignition coil controlled by the driver that set P0354 and install it in another coil location that did not have a DTC against it. Turn the ignition on, erase DTCs, then start and run the engine for up to one minute. If the engine will not start, crank the engine three times for 10 seconds. Read the codes again. If a correlating fault sets for the new coil location, replace the ignition coil, replace and program the PCM, then verify the repair and confirm the code stays gone. If the fault does not follow to the new location, continue to connector and terminal checks.
Inspect PCM, harness, and related connections
At this point, perform any applicable service bulletins and inspect the related PCM, inline, and component connections. Disconnect the PCM connectors, any related inline connectors, and the related component connectors. Look for improper seating, damaged locks, corrosion, water intrusion, weather seal damage, bent terminals, overheated or discolored terminals from poor connection, terminals pushed back in the cavity, spread terminals, and weak terminal tension. Repair anything you find. Then reconnect everything fully and make sure the connector locks are engaged. Erase the codes, test drive or operate the vehicle under the monitor conditions, and read codes again. If P0354 returns after those connection checks, replace and program the PCM, then verify the repair and confirm the code stays gone. If it does not return, the wiring or poor connection problem has been repaired.
Close with the takeaway
The key with P0354 is to prove the feed, prove the coil 4 control circuit, check the plug and coil path, and only move toward the PCM after the circuit and coil checks support it. Keep verification separate at the end, and make sure the code stays gone under the same operating conditions. For more diagnostic training, visit stepdiagnostics.com.
Final check
A clean diagnosis often comes from confirming the code first, then separating power feed, control circuit, coil and plug condition, connection integrity, and final repair verification.
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