Ignition Coil H Primary/Secondary Circuit Malfunction
The P0358 code indicates a malfunction in the primary or secondary circuit of ignition coil H (typically coil #8 on V8 engines). This circuit includes the coil itself, wiring, connectors, and the engine control module (ECM) driver. The ECM detects an electrical fault such as an open, short, or excessive resistance, preventing proper spark generation. This can lead to misfires, reduced power, and increased emissions.
01. Most Common Causes
- Faulty ignition coil H
- Open or shorted wiring in the coil circuit
- Poor electrical connection at coil or ECM
- Failed ECM driver for coil H
02. Symptoms You Will Notice
- Engine misfire (cylinder 8)
- Check Engine Light on
- Rough idle or hesitation
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0358 is present. Check for additional misfire codes.
Step 2: Visually inspect ignition coil H wiring and connector for damage, corrosion, or loose pins.
Step 3: Swap coil H with a known good coil from another cylinder. Clear codes and test drive. If code moves to the new cylinder, replace coil H.
Step 4: If code remains on cylinder H, test power and ground at coil connector with a multimeter. Check for 12V on power wire and continuity to ground.
Step 5: If power and ground are good, test the ECM control signal wire for continuity and proper voltage (typically a 5V square wave). If signal is missing, suspect ECM failure.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the misfire can damage the catalytic converter and cause poor performance. Short trips to a repair shop are acceptable.
How much does it cost to fix?▼
Replacing an ignition coil typically costs $50-$150 for parts and labor. If wiring or ECM repair is needed, costs can be higher.