What Does P1218 Mean?
P1218 indicates a short-to-positive (B+) condition in the fuel injector circuit for cylinder 6. The ECM has detected unwanted positive voltage on the cylinder 6 injector control line, which may cause the injector to fire continuously or erratically. This results in over-fueling of cylinder 6, potentially causing engine damage and catalytic converter overheating.
Safety Warning
A continuously firing injector can hydro-lock the engine, causing catastrophic mechanical damage. Excess fuel dumps into the exhaust and rapidly overheats the catalytic converter, presenting a serious fire risk.
Common Causes
30%
Wiring harness short to power from an adjacent hot circuit near cylinder 6
25%
Internally shorted cylinder 6 fuel injector
20%
Corroded connector with pin-to-pin cross-contamination at the injector plug
15%
Aftermarket installation or repair creating an unintended power feed
10%
ECM driver circuit failure holding the output high
Diagnostic Steps
1
Review freeze frame data and check for companion codes including P0306, P0172 (rich condition), or P1213.
2
Disconnect the cylinder 6 injector and measure voltage on the control wire with key-on engine-off. There should be no voltage when the injector is not being commanded.
3
Trace the cylinder 6 injector harness routing and inspect for chafing, melting, or contact with positive voltage wires, especially near the rear of the engine.
4
Measure the injector coil resistance and check for internal shorts between the coil and the power supply terminal.
5
Isolate whether the B+ voltage is coming from the harness side or the ECM side by disconnecting both ends and testing each segment.
6
Repair the wiring fault or replace the shorted injector, clear codes, and confirm repair with a road test monitoring cylinder 6 fuel trim.
Estimated Repair Cost
$175 - $650
Parts + labor, varies by vehicle and location
P1218 indicates a short-to-positive (B+) condition in the fuel injector circuit for cylinder 6. The ECM has detected unwanted positive voltage on the cylinder 6 injector control line, which may cause the injector to fire continuously or erratically. This results in over-fueling of cylinder 6, potent...
The most common cause of P1218 (Injector Circuit Cylinder 6 Short To Positive) is: Wiring harness short to power from an adjacent hot circuit near cylinder 6
Typical repair costs for P1218 range from $175 to $650, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A continuously firing injector can hydro-lock the engine, causing catastrophic mechanical damage. Excess fuel dumps into the exhaust and rapidly overheats the catalytic converter, presenting a serious fire risk.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1218 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel Injection System
Difficulty
Type
Manufacturer
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