Sensor internally faulty or shorted, giving a falsely hot reading; Signal wire chafed and shorted to ground or to the sensor ground wire; Water ingress or corrosion in the sensor connector or wiring plug; Damaged or pinched harness near the front bumper, grille or engine bay where the sensor is often mounted; Poor or shared ground connection affecting the sensor circuit; Fault in the control unit's sensor input circuit.

P00DB

Ambient Air Temperature Sensor Circuit B Low.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
DB: FaultThe specific fault in that area

What it means

P00DB means the engine control unit has seen the signal from the second ambient air temperature sensor circuit (circuit B) fall below its expected electrical range. The sensor normally works on a reference voltage that changes with temperature. A low signal suggests a short to ground, a short inside the sensor, or a fault in the wiring. Which sensor is circuit B, and where it is fitted, depends on the model.

Symptoms

Engine management light on
Ambient or outside temperature display showing an implausibly high value, or dashes
Climate control or automatic air conditioning behaving oddly
Slightly rough running or altered idle on some models in cold or hot conditions
Possible poor cold start or fuelling adjustments where the ECU uses ambient temperature as a correction

Possible causes

Sensor internally faulty or shorted, giving a falsely hot readinglikely
Signal wire chafed and shorted to ground or to the sensor ground wirelikely
Water ingress or corrosion in the sensor connector or wiring pluglikely
Damaged or pinched harness near the front bumper, grille or engine bay where the sensor is often mountedpossible
Poor or shared ground connection affecting the sensor circuitpossible
Fault in the control unit's sensor input circuitrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting the ambient temperature reading when the fault set and whether other temperature sensor codes are present.
Compare the live ambient temperature value with the real outside temperature and with the intake air temperature on a cold engine; a very high or fixed reading points to a low-voltage circuit fault.
Find the circuit B sensor using the model-specific wiring diagram, then inspect the sensor, connector and harness for damage, rubbing, water or corrosion.
With the connector unplugged, check the live value: it should fall to a very cold or default reading. If it stays hot, the wiring between the sensor and control unit is likely shorted to ground.
Measure the reference voltage and ground at the connector against the manufacturer's specification.
Test the sensor resistance at a known temperature and compare it with the specification for that model.
Check the signal wire for continuity and for a short to ground with the control unit disconnected, following the wiring diagram.
Wiggle-test the harness with live data displayed to find any intermittent short.

How to fix

Replace the ambient air temperature sensor if its resistance is out of specification or it reads falsely hot.
Repair or replace the chafed or shorted section of wiring, and secure it so it cannot rub again.
Clean, dry and repair corroded or damaged connector terminals, or replace the connector.
Repair any poor ground connection found on the circuit.
Only after all other causes are ruled out, diagnose and repair or replace the control unit, following the manufacturer's procedure.

Can I keep driving?

Low severity

The car can normally be driven while you book it in, as this fault usually affects only temperature readings and minor corrections. Have it fixed soon, because a wiring short can lead to other faults and the warning light may mask new problems.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.