P0357 Code: Ignition Coil G Primary/Secondary Circuit
Coil G, which fires cylinder 7 on V8s, has an electrical fault. On GM trucks it sits by the brake booster.
At a glance
Severity: Moderate
- Meaning
- Ignition Coil G Primary/Secondary Circuit
- System
- Ignition & Misfire · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $30–$1,600
- DIY difficulty
- Moderate
P0357 means the engine computer's seventh coil output did not show the primary current or feedback it expects when it fired. In practice this code belongs to V8 engines, plus the odd V10 or V12. GM and Chrysler count odd cylinders down the driver side, so cylinder 7 is the rear driver-side cylinder, tucked beside the brake booster on GM trucks and SUVs. Ford counts the driver bank 5 to 8, which puts cylinder 7 third from the front on that side. The rear corners of a V8 run hottest, and on GM engines with the coils mounted on the valve covers, the short plug wire from coil G to plug 7 passes close to the exhaust manifold. That is why the secondary side, not just the coil, needs checking.
Can I keep driving? Driving gently to a shop is usually fine, but do not tow or haul while a cylinder is dead. A flashing light means stop, because the catalytic converter on that bank is overheating.
How to read P0357
- P Powertrain
- 0 Generic (SAE)
- 3 Ignition / misfire
- 57 Specific fault
Symptoms
- Rough idle and a noticeable shake in a pickup or large SUV
- Check-engine light with P0307, flashing when towing or climbing
- Misfire that is worse after a long tow or on hot days
- Burned smell or a scorched plug wire boot at the rear driver-side corner
- Uneven exhaust note from the driver-side tailpipe on dual exhausts
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Coil G has failed internally
- Plug wire or boot from coil G to plug 7 burned on the exhaust manifold (GM V8s with valve-cover coils)
- Coil G connector or harness chafed at the rear of the valve cover or the firewall
- Feed or ground shared by the coils on cylinder 7's bank has a poor connection
- Worn plugs and heavy towing heat overloading the coil
- On early 5.7L Hemis, the companion coil or wire between cylinders 4 and 7 has failed
- Coil G driver in the engine computer has failed
Diagnosis step by step
Find cylinder 7 on your V8
On GM and Chrysler V8s it is the rear cylinder on the driver side, next to the brake booster on trucks. On a Ford V8 it is third from the front on the driver side. On GM trucks, access is easier with the air intake duct removed and a long extension used from above.
Tools: Flashlight
Look for a bank pattern
List every coil and misfire code. Several codes on odd cylinders of a GM V8, or on cylinders 5 to 8 of a Ford V8, point to the shared feed or ground for that bank. A single P0357 points to coil G, its wire or its connector.
Tools: OBD-II scanner
Inspect the plug wire and boot
On engines where coil G feeds plug 7 through a short wire, pull the wire and look for a scorched boot, a missing heat sleeve or a white burn mark where it touched the manifold. Measure its resistance end to end and compare it with the cylinder 5 wire. An open reading or a value far above its neighbor means the wire must be replaced.
Tools: Multimeter, Flashlight
Check the companion cylinder on early Hemis
The 5.7L Hemi has two plugs per cylinder, and on earlier versions each coil also fires a plug in its companion cylinder through a wire. Cylinders 4 and 7 are companions, so inspect both plugs and the lead on cylinder 4 as well.
Tools: Spark plug socket, Flashlight
Swap coil G with coil 5
Swap coils 7 and 5, which are on the same bank for GM and Chrysler. Clear the codes and drive with some load. If the fault moves to P0355 the coil is bad. If it stays on 7, the wire, connector or harness is at fault.
Tools: Screwdriver, OBD-II scanner
Protect the repair from heat
Route the new wire exactly as the factory did, in its clips, and fit a heat sleeve or boot shield if the engine uses them. A wire that sags onto the manifold will burn through again within weeks.
Tools: Pliers, Gloves
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace coil G | Yes | $90–$280 |
| Replace plug wire and heat sleeve on cylinder 7 | Yes | $30–$150 |
| Replace plugs and wires on the bank (tow vehicles) | Yes | $200–$500 |
| Repair coil G harness at the firewall | No | $120–$350 |
| Replace engine computer (rare) | No | $700–$1,600 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Ram
The 5.7L Hemi's firing order makes cylinders 4 and 7 companions. On earlier versions, where each coil also fires the neighboring cylinder's second plug through a wire, a P0357 with a misfire on cylinder 4 usually means the coil G wire or the cylinder 4 plug it feeds, not a second coil failure.
Emissions / smog test impact
Will fail
A stored P0357 with the check-engine light on fails an OBD-II emissions test. Heavy-duty pickups over the weight limit are exempt from testing in many states, so check your state's rules, but the fault should be fixed either way.
Frequently asked questions
Where is cylinder 7 on my truck?
On GM and Ram V8s it is the rear cylinder on the driver side, near the brake booster. On Ford V8s, which count the driver bank 5 to 8, it is the third cylinder back on the driver side.
Does heavy towing kill ignition coils?
It speeds up wear. Towing means high cylinder pressure and a very hot engine bay, and the rear corners of a V8 get the least airflow. Keeping plugs fresh on a tow vehicle is the best way to protect the coils.
Why does my Hemi show P0357 together with a cylinder 4 misfire?
Because on earlier Hemis, the coil on one cylinder fires the second plug of its companion cylinder, and cylinders 4 and 7 are companions. Check the wire and plug on cylinder 4 before replacing a second coil.
Can I replace just the plug wire?
If the coil tests fine and only the wire or boot is burned, yes. Fit a heat sleeve and route it exactly in the original clips, otherwise the new wire will fail the same way.