P218B code meaning
Throttle/Fuel Inhibit B Circuit
Powertrain system Generic code P21xx codes Check engine light
What P218B means
P218B is a general electrical fault in the second throttle/fuel inhibit line, B. An inhibit line carries a signal with which another unit can tell the engine computer to keep the throttle closed or stop fuelling. No manufacturer documents the B line publicly. The only published use of this function concerns the A line: GM's 2005 table for the 3.5-litre V6 (L66) places it in the throttle valve control section, where the injection and throttle processors check each other, and monitors it with P2553-P2555 once per drive cycle after ignition off, lighting the MIL on the next drive cycle. California's OBD rule requires inputs of this kind to be checked for circuit faults. Open wires, corroded pins and module connector faults come first; reduced power is possible.
P218B at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P218B
- Check engine lamp on the following drive
- Possible power limitation
Common causes of P218B
- Most likelyOpen or high-resistance inhibit B wire
- PossibleCorroded or loose pins at the engine or throttle module connector
- Less likelyFault in the unit that drives the inhibit signal
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Throttle fuel inhibitWiring harness
What each part of P218B 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. |
| 8B | The exact fault in that area. |
What to do next
- Note P218B 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 P218B
What does P218B mean?
P218B means "Throttle/Fuel Inhibit B Circuit". P218B is a general electrical fault in the second throttle/fuel inhibit line, B. It is a generic code, so it means the same on every make.
Is it safe to drive with P218B?
Drive gently and only to a workshop. With P218B the car can go into limp mode (reduced power) to protect itself.
Will P218B fail an emissions test?
Yes, it can. P218B 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 P218B to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P218B 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.