P218D code meaning
Throttle/Fuel Inhibit B Circuit Low
Powertrain system Generic code P21xx codes Check engine light
What P218D means
P218D reports that the voltage on inhibit line B sits below the lowest permitted value, which normally points to a short to ground, a missing supply from the sending unit or an open line pulled down by the input stage. No manufacturer documents P218D publicly. For the A line, GM's 2005 table for the 3.5-litre V6 (L66) gives a concrete limit: P2554 is set when the analogue throttle inhibit circuit reads under 0.498 V for 4 seconds, with the check running after ignition off and the MIL lit on the next drive cycle. California's OBD rule requires out-of-range checks on such inputs. Chafed insulation touching body ground, water in a connector or a failed driver in the sending module are the likely causes. P218E is the opposite fault, P218B the general circuit code.
P218D 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 P218D
- Check engine lamp on the following drive
- Possible power reduction
Common causes of P218D
- Most likelyInhibit B wire shorted to ground
- PossibleWater or corrosion in a connector of the inhibit line
- Less likelyOutput stage of the sending module failed
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 P218D 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. |
| 8D | The exact fault in that area. |
What to do next
- Note P218D 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 P218D
What does P218D mean?
P218D means "Throttle/Fuel Inhibit B Circuit Low". P218D reports that the voltage on inhibit line B sits below the lowest permitted value, which normally points to a short to ground, a missing supply from the sending unit or an open line pulled down by the input stage. It is a generic code, so it means the same on every make.
Is it safe to drive with P218D?
Drive gently and only to a workshop. With P218D the car can go into limp mode (reduced power) to protect itself.
Will P218D fail an emissions test?
Yes, it can. P218D 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 P218D to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P218D 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.