← Back to list

2004 Dodge Intrepid 2.7L P0356 Fault: Ignition Coil F Primary/Secondary Circuit Diagnosis and Fix

Model: 2004 Dodge Intrepid Fault Code: P0356 Posted: 2017-08-05 21:12

Initially, I received a P0141 O2 Sensor Heater Circuit (Bank 1, Sensor 2) code. After replacing the sensor, the code returned. To isolate whether the original sensor was faulty, I swapped Bank 1 Sensor 2 with Bank 2 Sensor 2. During the road test, the check engine light reappeared, and a new code appeared: P0356 — Generic Ignition Coil F Primary/Secondary Circuit. Are these two codes related? I tested for spark on cylinder #6 and found no spark, while other cylinders showed normal spark. When I removed the faulty coil and connected it to a working coil location, spark was restored—indicating that the ignition coil itself is not defective. Testing voltage on the green wire (power supply) at the coil connector showed 12V with the test light lit. However, when measuring the signal wire (orange), I observed only 0.22V under KOEO conditions. This suggests a potential issue in the control circuit. I have verified that all other sensors show consistent voltage readings and no short circuits were detected using a multimeter. However, when I removed the 40A horn/park fuse, the test light went out—indicating a possible short to ground or load in the power circuit. This behavior points to an underlying wiring fault. I am seeking clarity on the correct wire colors (e.g., dark green with light green tracer for DG/LG) and guidance on how to properly diagnose the ignition coil control circuit, especially regarding voltage presence at the coil connector when unplugged under KOEO conditions.

Related fault codes
P0356
Comments (9)
Anonymous 2017-08-06 07:31

For P0141, did you verify the heater circuit wiring? Note: Aftermarket O2 sensors—especially DIY types—are known to cause issues. Under KOEO (Key On Engine Off), does the DG/LG wire have 12V? Is there 12V on the TN/LB wire (coil control signal)? When the coil is unplugged, check that the control circuit has no voltage and is not grounded. Also inspect the coil electrical connector for damage or corrosion.

Anonymous 2017-08-06 09:46

Thanks for your reply. I did test the P0141 heater circuit—measured 4.12V at the harness end of all sensors. While this is below the expected 12V, I assumed it was acceptable since other sensors (not showing issues) are receiving similar voltage. What does TN/LB refer to? On my vehicle, the wires to the coil are orange and green. Online references indicate that green is power and orange is the signal wire.

Anonymous 2017-08-06 10:19

The 4.8V reading was from the signal wire—this appears more like a 5V reference voltage, not heater circuit voltage. Was this an aftermarket or DIY O2 sensor? Regardless, both control and signal circuits are affected. TN/LB refers to specific wire colors—see attached diagram. Color confusion is common. Confirm that when the ignition coil is unplugged under KOEO conditions, there is no voltage on the control wire and it is not grounded.

Anonymous 2017-08-08 18:16

The 4.8V was measured on the signal wire, not the heater circuit. Under KOEO, I measure only 0.22V on the coil’s control circuit (TN/LB).

Anonymous 2017-08-09 08:09

Under KOEO, when the ignition coil is unplugged, check for voltage on the DK/LG wire. Test multiple coils—this will help identify if the issue is isolated to cylinder #6 or affects all cylinders. If only cylinder #6 shows a problem, the wiring between the ECU and that coil may be faulty. Check the connector and several inches of cable leading back from the coil—this area is prone to wear or damage.

Anonymous 2017-08-11 21:01

What does DK/LG mean? I tested all connectors and found consistent results: no 12V anywhere (on O2 sensors or other components). I suspect a short somewhere in the vehicle. The test light went out when I removed the 40A horn/park fuse—this suggests a possible short to ground in that circuit. Do you have a wiring diagram showing where this circuit is located? Also, please specify wire colors clearly—for example: dark green with light green tracer, etc.

Anonymous 2017-08-12 08:43

DG/LG refers to dark green with a light green tracer. Are your coil wires different in color than described? Are you confident in performing electrical troubleshooting? Which specific circuit do you need a diagram for—for example, the PDC section requires fuse H.

Anonymous 2017-08-13 16:31

I'm trying to locate the short. The test light went out when I removed the horn/park fuse—this indicates a load or ground fault in that circuit. Where should I begin troubleshooting from?

Anonymous 2017-09-11 16:55

The issue has been resolved—the root cause was a loose PCM connector, which caused intermittent signal loss and false codes.