Technical Description of OBD-II Trouble Code
Correlation between Charge Air Temperature and Intake Air Temperature in Bank 1
What does that signify?
This generic powertrain diagnostic trouble code (DTC) is applicable to all OBD-II vehicles, including Nissan, Toyota, Chevrolet, GMC, Ford, Dodge, Vauxhall, etc. The exact repair steps may vary depending on the make and model, despite being a generic code.
A stored code P011C indicates that the powertrain control module (PCM) has detected a discrepancy in the signals between the charge air temperature (CAT) sensor and the intake air temperature (IAT) sensor for engine bank number one.
Bank 1 refers to the engine bank that contains the number one cylinder. As evident from the code description, this code is only used in vehicles equipped with forced air induction devices and multiple intake air inlet sources. Throttle bodies are referred to as intake air inlet sources. Forced air induction devices include turbochargers and superchargers.
CAT sensors typically consist of a thermal resistor that extends from the housing on a wire pedestal. The resistor is positioned in a way that allows ambient air entering the engine intake, after leaving the intercooler (also known as the air charge cooler), to flow across it. The housing is usually designed to thread or bolt into a turbocharger/supercharger inlet pipe, near the intercooler. As the charge air temperature rises, the resistance level in the CAT resistor decreases, causing the circuit voltage to move towards the reference maximum. The PCM interprets these variations in CAT sensor voltage as changes in charge air temperature.
The CAT sensor/s provides data to the PCM for the operation of the boost pressure solenoid and boost pressure release valve, as well as certain aspects of fuel delivery and ignition timing calculation.
The IAT sensor functions in a similar manner to the CAT sensor. In fact, some early computerized vehicle service manuals (pre OBD-II) referred to the intake air temperature sensor as an air charge temperature sensor. The IAT sensor is positioned so that ambient intake air passes across it as it enters the engine intake. The IAT sensor is usually located near the air filter housing or air inlet pipe.
A code P011C will be stored and a malfunction indicator lamp (MIL) may illuminate if the PCM detects voltage signals from the CAT sensor and the IAT sensor that differ by more than a preprogrammed degree. Multiple ignition cycles with a failure may be required for MIL illumination.
What is the severity of this DTC?
The conditions contributing to a stored code P011C can adversely affect overall engine performance and fuel efficiency, making it a severe issue.
What are some of the symptoms of the code?
Symptoms of a P011C trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P011C diagnostic steps?
Before attempting to diagnose a code P011C, it is recommended to have access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source.
When diagnosing any CAT sensor related code, start by ensuring that there are no obstructions in the airflow across the intercooler.
If there are no intercooler obstructions and the air filter is relatively clean, visually inspect all CAT/IAT system wiring and connectors. Make necessary repairs as required.
Next, connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. Freeze frame data can be described as a snapshot of the exact circumstances that were occurring at the time of the malfunction leading to the stored code P011C. It is advisable to write down this information as it may be helpful during the diagnosis process.
Clear the codes and test-drive the vehicle to see if the code is reset.
If the code is reset:
If all the sensors comply with the manufacturer’s specifications:
If reference voltage and a ground are present:
If the sensor signal circuit reflects the correct degree of voltage:
If all CAT/IAT sensors and circuits are within specifications, suspect PCM failure or a PCM programming error.
