Fuel and air

P00A4 — Charge Air Cooler Temperature Sensor Signal Erratic (Bank 2)

Severity: medium Drive with care, to a shop

What P00A4 means

The engine control module monitors the temperature of the air leaving the charge air cooler (intercooler) using a thermistor sensor. P00A4 means the bank 2 sensor signal is dropping out or jumping around in a way that doesn't match real temperature changes. The ECM uses this data to calculate boost, fueling and engine protection.

Symptoms

  • Check Engine light on
  • Hesitation or sluggish acceleration under load
  • Lower fuel economy
  • Reduced power or limp mode under heavy load
  • Jumpy charge air temperature readings on a scan tool

Possible causes

  1. Failed bank 2 charge air cooler temperature sensor
  2. Damaged, chafed or corroded wiring or connector terminals
  3. Poor sensor ground or a problem with the 5 V reference supply
  4. Moisture or oil contamination in the connector
  5. ECM fault (rare)

How to diagnose

  1. Scan for codes and freeze frame data, and look for other temperature or boost-related codes
  2. Watch bank 2 charge air temperature live and compare it with bank 1 and ambient temperature
  3. Inspect the sensor, connector and harness for chafing, corrosion, oil and loose locks
  4. Wiggle the harness and connector with the engine running and watch for signal spikes
  5. Check reference voltage and ground at the connector with a multimeter
  6. Measure sensor resistance and compare to the spec at different temperatures
  7. Test the wires between the sensor and the ECM for opens and shorts
  8. If the sensor and wiring are good, have the ECM tested

Common fixes

  • Replace the charge air cooler temperature sensor
  • Repair or replace damaged wiring and the connector, and clean the terminals
  • Restore the sensor ground or reference supply
  • Reflash or replace the ECM only after it is confirmed faulty

Questions and answers

Can I drive with P00A4?

Briefly and carefully, for example to a shop. Avoid heavy loads, since the ECM may limit power and bad temperature data hurts engine performance.

What most often causes P00A4?

Usually the sensor itself or a poor connection in its connector or wiring. Inspect the connector and harness first, then test the sensor signal.

Do I need a new ECM for P00A4?

Almost never. An ECM fault is unlikely, so check the sensor, wiring, reference voltage and ground first.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.