P0358
Ignition Coil H Primary/Secondary Circuit
When a vehicle powertrain module registers the fault code P0358, it points directly to an internal system malfunction identified as "Ignition Coil H Primary/Secondary Circuit". Operating your engine under this condition may degrade long-term fuel maps.
Driver's Summary
When your OBD2 scanner shows P0358, the engine control module has flagged an issue specifically related to ignition coil h primary/secondary circuit. The most common signs are v8 engine misfire, significant power loss, vibration. Stop driving as soon as it is safe to do so. This fault can lead to expensive secondary damage if left unaddressed.
Symptoms
V8 engine misfire, significant power loss, vibration
Common Causes
- Dead ignition coil H (Cylinder 8)
- Wiring damage due to exhaust heat
- Fouled spark plug
- Failed coil driver in PCM
How to Fix
- 1 Replace ignition coil H
- 2 Repair and heat-shield wiring
- 3 Replace spark plug
- 4 Replace PCM
Technical Explanation
P0358 is stored after the control module confirms the fault over multiple ignition cycles, ruling out transient electrical noise as the cause. For injector-specific codes, the ECM monitors the injector control circuit voltage drop during each pulse; a shorted or open injector presents a characteristic resistance signature that differs measurably from a healthy unit. Once confirmed, the code is stored as a permanent DTC and the MIL is activated. The freeze frame snapshot — recording RPM, load, coolant temperature, and fuel trim at fault detection — is also saved and is critical for accurate diagnosis.
Is It Safe to Drive?
With P0358 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to dead ignition coil h (cylinder 8).
Mechanic's Pro Tip
Module replacement should always be the last resort for P0358 after exhaustively verifying all power supply circuits, ground connections, and communication bus wiring. Use a wiring diagram to locate all fuses, relays, and ground points for the affected module, and measure voltage drop on each ground with the circuit loaded. A module "failure" is frequently a corroded ground eyelet or a weak battery causing brownout conditions — fix these first and you'll save hundreds of dollars on an unnecessary module replacement.
Ignition coil: $80 - $200