P218C code meaning
Throttle/Fuel Inhibit B Circuit Range/Performance
Powertrain system Generic code P21xx codes Check engine light
What P218C means
P218C means the inhibit B line is electrically within limits, yet its state or response does not fit what the controller expects: it may signal a lock when none is requested, or fail to react during a function test. No manufacturer documents P218C publicly. GM's 2005 table for the 3.5-litre V6 (L66) shows the analogous test on line A as P2553: a function check of the relay path, judged by a normal signal on the serial data link with battery voltage above 7 V, run once per drive cycle after ignition off and lighting the MIL on the next drive. California's OBD rule asks for plausibility checks of such inputs. Likely causes are a sticking relay, a slow-switching driver or software mismatch between the modules. P218D/P218E cover hard low and high faults.
P218C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P218C
- Check engine lamp on the next drive
- Occasional power reduction without obvious reason
Common causes of P218C
- PossibleRelay in the inhibit path sticking or switching late
- PossibleSoftware versions of the communicating modules do not match
- PossibleIntermittent contact causing implausible line states
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Throttle fuel inhibit
What each part of P218C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 1 | Area: fuel and air metering. |
| 8C | The exact fault in that area. |
What to do next
- Note P218C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P218C
What does P218C mean?
P218C means "Throttle/Fuel Inhibit B Circuit Range/Performance". P218C means the inhibit B line is electrically within limits, yet its state or response does not fit what the controller expects: it may signal a lock when none is requested, or fail to react during a function test. It is a generic code, so it means the same on every make.
Is it safe to drive with P218C?
Drive gently and only to a workshop. With P218C the car can go into limp mode (reduced power) to protect itself.
Will P218C fail an emissions test?
Yes, it can. P218C is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P218C to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P218C clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.