Technical Description of OBD-II Trouble Code
Circuit Range/Performance Issue with Turbocharger/Supercharger Inlet Pressure Sensor (Downstream of throttle valve)
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to vehicles equipped with OBD-II and have a turbocharger or supercharger inlet pressure sensor. This includes various brands such as Ford, Dodge, Saturn, Nissan, Subaru, Honda, etc. Although it is a generic code, the specific repair steps may vary depending on the make, model, and engine.
This particular code indicates a malfunction in the Turbo/Supercharger Inlet Pressure Sensor (TCIP) circuit, specifically related to its range or performance. The turbo/supercharger is responsible for increasing the “volumetric efficiency” (amount of air) in the combustion chamber by creating pressure in the intake system.
In general, turbochargers are exhaust driven and superchargers are belt driven. The inlet of the turbo/supercharger is where they draw filtered air from the air filter. The inlet sensor works with the ECM (Electronic Control Module) or PCM (Powertrain Control Module) to monitor and regulate intake pressure.
The “(Downstream of throttle valve)” indicates the specific inlet sensor that has the malfunction and its location. The pressure sensor may also include a temperature sensor.
This trouble code is closely related to P012A, P012C, P012D, and P012E.
What are some of the symptoms of the code?
Symptoms of a P012B engine code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some of the troubleshooting steps?
It is recommended to check for technical service bulletins (TSBs) for your specific vehicle. Accessing a known fix can save time and money during diagnosis.
For example, there is a known bulletin for 2013 Ford F-150 pickups with the 3.5L EcoBoost V6 engine, identified as Ford TSB 14-0082. If you have a P012B and/or P012D code with that vehicle, refer to the bulletin for the full details and recommended fix.
Some basic tools that are useful when working with electrical systems include an OBD code reader, multimeter, basic socket set, basic ratchet and wrench sets, basic screwdriver set, rag/shop towels, battery terminal cleaner, and a service manual.
When working on the vehicle, it is important to follow safety tips such as letting the engine cool, chalking the wheels, and wearing personal protective equipment (PPE).
Basic Step #1
Visually inspect the TCIP and its surroundings. Given the nature of these codes, there is likely a physical problem causing the issue. Check the wiring harness thoroughly, as it often runs along areas with high temperatures. To locate the malfunctioning sensor’s circuit, refer to “Downstream of Throttle valve.” Downstream refers to the side closer to the intake manifold, typically where the throttle valve is mounted. Follow the wires from the TCIP and inspect for any frayed, chafed, or cut wires that may be causing an issue. If accessible, disconnect the sensor’s connector and inspect the pins for corrosion.
NOTE: Green color indicates the presence of corrosion. Also, visually inspect all ground straps and look for corroded or loose ground connections. A problem within the general electrical system can cause drivability issues and poor mileage, among other unrelated problems.
Basic Step #2
Depending on the vehicle’s make and model, there may be a fuse related to the circuit. Fuse boxes can be located in various places, such as under the dash, behind the glove box, under the hood, or under a seat. Locate the fuse and ensure it fits tightly in the slot and is not blown.
Basic Tip #3
Check the air filter! Visually inspect the air filter for signs of clogging or dirtiness. A clogged filter can cause a low-pressure condition. If the air filter is clogged or damaged (e.g., water intrusion), it should be replaced. This is a cost-efficient way to rule out the filter as the cause, as air filters are often inexpensive and easy to replace.
NOTE: Check if your air filter is cleanable. If so, you may be able to clean it instead of replacing the entire assembly.
Basic Step #4
If everything checks out at this point and a malfunction cannot be found, it is recommended to verify the circuit itself. This may involve disconnecting the ECM or PCM electrical connector (ensure the battery is connected) and performing basic electrical tests on the circuit (e.g., checking for continuity, checking for short to ground, checking power, etc.). Any open or short indicates a problem that needs to be repaired. Good luck!
