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Technical Description of OBD-II Trouble Code
Circuit for Ambient Air Temperature Sensor
What does that signify?
This particular diagnostic trouble code is applicable to all engines equipped with OBDII, but it is more commonly found in certain Audi, BMW, Chrysler, Dodge, Ford, Jeep, Mazda, Mitsubishi, and VW vehicles.
The Ambient Air Temperature (AAT) sensor converts the ambient air temperature into an electrical signal for the Powertrain Control Module (PCM). This input is used to adjust the operation of the air conditioning system and display the outside air temperature.
The PCM receives this input along with possibly two more inputs: Intake Air Temperature (IAT) and Engine Coolant Temperature Sensor (ECT). When the ignition switch is first turned on after a long cool down period, the PCM compares the AAT sensor voltage to the IAT/ECT sensor readings. If these inputs vary too much, this code is set. It also examines the voltage signals from these sensors to determine their accuracy when the engine is fully warmed up.
This code is typically triggered by electrical issues. The troubleshooting steps may vary depending on the manufacturer, type of AAT sensor, and wire colors.
Symptoms
The symptoms may include:
Causes
Possible causes of a P0070 trouble code may include:
Possible Solutions
A good starting point is to check for technical service bulletins (TSB) specific to your vehicle. Your issue may be a known problem with a known solution provided by the manufacturer, which can save you time and money during diagnosis.
Next, locate the AAT sensor in your vehicle. This sensor is usually located in front of the radiator behind the grille or front bumper area. Once found, visually inspect the connectors and wiring. Look for any scraping, rubbing, bare wires, burn spots, or melted plastic. Separate the connectors and carefully examine the terminals inside. Check for any signs of burning or green tint indicating corrosion. If needed, clean the terminals using electrical contact cleaner and a plastic bristle brush. Allow them to dry and apply electrical grease to the contact points.
The most common failure is related to connections, with a failed sensor being the second most common due to its harsh environment.
While checking the connections, you can test the sensor using a Digital Volt-Ohm Meter (DVOM). With the ignition switch off, disconnect the sensor and connect the Red (Positive) lead of the DVOM to one post on the sensor and the Black (Negative) lead to the other post. Determine the temperature of the sensor (the outside temperature) and compare it to the resistance on the chart. The DVOM should display the corresponding resistance in ohms. A reading of either 0 ohms or infinite resistance (usually indicated by the letters OL) indicates a failed sensor.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if this code reappears. If it does not, then the issue was most likely related to the connections.
If the P0070 code does reappear, further testing of the AAT sensor and its associated circuits is necessary. Typically, there are 2 wires connected to the AAT sensor. With the ignition switch off, disconnect the harness going to the AAT sensor. Turn the ignition switch on and use a scan tool to access PCM data (assuming the PCM is the module receiving the AAT sensor input). Read the AAT sensor temperature or voltage. It should read 5 volts or a value other than the ambient air temperature (which is a very low temperature) in degrees. Next, turn the ignition switch off, connect a jumper wire across the two terminals inside the harness connector going to the AAT sensor, and then turn the ignition switch on. It should read close to 0 volts or a value other than the ambient air temperature (which is a very high temperature) in degrees. If there is no 5 volts to the sensor or if you see no change, repair the wiring from the PCM to the sensor or consider the possibility of a faulty PCM.
If all previous tests have passed and you continue to receive a P0070 code, it most likely indicates a failed AAT sensor. However, a failed control module cannot be ruled out until the AAT sensor has been replaced. If you are unsure, seek assistance from a trained automotive diagnostician. PCMs must be programmed or calibrated to the vehicle in order to be installed correctly.
Professional Service
While we always recommend resolving this issue through mechanical means, if that is not possible, we offer the option to permanently delete this specific DTC. All other codes will continue to function. If you are interested in this option, please upload your ECU file to our portal.
