# P0021 — Generic Powertrain — Fuel & Air Metering / Aux Emission Controls

> ClearTheCode diagnostic code reference (not OEM service data).

Source: https://clearthecode.com/codes/P0021

**System:** Powertrain · Fuel & Air Metering / Aux Emission Controls

**Severity:** moderate

## Description

Generic fuel, air metering, or auxiliary emission control circuit fault. Inspect the relevant sensor, actuator, and circuit indicated by the code's manufacturer-specific definition.

## Diagnostic snapshot

- **Difficulty:** 6/10 — Intermediate diagnostics
- **Est. repair cost:** $120 – $450

## Diagnostic workflow

1. Confirm P0021 with a live scan — note pending vs stored and freeze frame data.
2. Inspect wiring/connectors and related sensors before replacing modules.
3. Clear codes and road-test; re-scan after two drive cycles if the monitor must set.