Throttle/Fuel Inhibit Circ Low
The PCM has detected a malfunction in the throttle or fuel inhibit circuit. This type of code is much more prominent in diesel powered vehicles.
Code Set Parameters
Abnormal voltage readings in the throttle or fuel inhibit circuit (that vary by greater than 10-percent of the manufacturer's referenced voltage) will cause a code to be stored and a malfunction indicator lamp to be illuminated. These abnormal readings are detected by the PCM and/or fuel injection control module.
A stored code and illuminated service engine soon lamp are normally accompanied by a NO-START condition or engine misfire. Other engine misfire, fuel injector, and fuel system pressure codes will usually accompany this type of code.
Likely causes include corroded or damaged connector pins in the fuel injection control module main connector or defective fuel injectors. Other causes include open, shorted, or damaged circuitry, connectors, or components.
Technicians report that the fuel supply system is often condemned in error when this code is exhibited.
- The throttle/fuel inhibitor circuit is typically integrated into the PCM or fuel control module in diesel powered applications
- Its purpose is to limit fuel supply or throttle activation if a fuel injector malfunction is detected
A scanner or code reader, a digital volt ohmmeter, and access to a manufacturer's wiring schematic will be necessary to successfully diagnose this code
Begin your diagnosis with a visual inspection of all wiring and connectors
- Repair or replace damaged, disconnected, shorted, or corroded wiring, connectors, and components as necessary
- Always retest the system after repairs are completed to ensure success.
If all system wiring, connectors, and components (Including fuses) appear to be in normal working order, connect the scanner (or code reader) to the diagnostic connector and record all stored codes and freeze frame data
- This information can be extremely helpful in diagnosing intermittent conditions that may have contributed to this code being stored
- After the codes are cleared, operate the vehicle to see if the code returns
- If the code fails to immediately return, you may have an intermittent condition
- Intermittent conditions can prove to be quite a challenge to diagnose and in extreme cases may have to be allowed to worsen before a correct diagnosis can be made.
Test voltage at the fuel injection control module to determine if there is sufficient power and ground when the ignition key is in the start position
- If the required voltage is present at the controller, then suspect an open circuit in the controller connector
- Repair the open circuit as required, clear the code, and test drive the vehicle to ensure that the repair has been successful
If there is no voltage at the controller (or reduced voltage is present) then the problem is likely in the electrical wiring or connectors
- Technicians have reported corroded electrical connector faces that fail when placed under the load of engine startup
- Some manufacturers also use fuel pump safety interrupter switches
- Check to make sure that this switch has not been activated before performing an extensive diagnosis for nothing
- Also be aware that plug-in type fuses can appear adequate when performing key-on-engine-off testing and fail when placed under the load of engine start-up
- It is critical that you test fuel pump and fuel injection related fuses under start-up conditions
- Repair or replace defective fuses as necessary, clear the code/s, and test drive the vehicle to ensure that a successful repair has been performed.
Should all circuits conform to manufacturer's specifications, suspect a defective PCM or fuel injector controller
- Failure of controllers is rare and will require reprograming.