P1167

What Does Code P1167 Mean?

DTC P1167 is a manufacturer-specific powertrain code that translates to “Invalid Test, Throttle Not Depressed.” This indicates that the Engine Control Module (ECM) or Powertrain Control Module (PCM) attempted to initiate a specific diagnostic self-test, but a critical prerequisite condition related to throttle position was not met. Specifically, the ECM requires the throttle to be in a non-depressed state (typically closed or at idle position) for the test to run accurately. When the ECM detects that the Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) sensor signal indicates throttle depression during this designated test window, it aborts the test, logs P1167, and illuminates the Malfunction Indicator Lamp (MIL). This essentially means the ECM received contradictory information: it needed a closed throttle but perceived an open throttle, rendering the intended diagnostic test inconclusive or invalid. This condition often prevents the completion of readiness monitors, which can affect vehicle emissions testing compliance.

Common Symptoms

• Malfunction Indicator Lamp (MIL) illumination: The primary and often only noticeable symptom.
• Incomplete readiness monitors: The vehicle may fail emissions inspections due to certain monitor tests not completing their required diagnostic cycles.
• No apparent driveability issues: In many cases, the underlying system intended for diagnosis might be fully functional, and the code only reflects an inability to run a specific test.
• Subtle idle instability or hesitation: If the TPS/APP sensor signal is genuinely erratic or incorrect, it might manifest as slight fluctuations in idle speed or minor responsiveness issues, although P1167 primarily concerns the test prerequisite.

What Causes the Code P1167?

• Faulty Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) sensor: A malfunctioning sensor that provides an erroneous voltage signal, indicating an open throttle position when the throttle is physically closed or at rest.
• Wiring harness issues: Damaged, chafed, shorted, or open circuits in the wiring leading to or from the TPS/APP sensor, causing incorrect signal transmission to the ECM.
• Corroded or loose electrical connectors: Poor electrical contact at the TPS/APP sensor or ECM connectors disrupting signal integrity.
• Physical throttle body malfunction: Mechanical issues such as a sticking throttle plate, excessive carbon buildup preventing full closure, or a miscalibrated throttle stop, which physically prevents the throttle from reaching its fully closed position, thereby affecting the TPS reading.
• ECM/PCM software glitch or internal fault: Although less common, an internal ECM fault or corrupted software can misinterpret correct sensor inputs or incorrectly initiate a test under inappropriate conditions.
• Vacuum leaks (indirect): Severe vacuum leaks could potentially influence engine load and air intake parameters, which might, in some rare cases, indirectly affect how the ECM interprets throttle position during specific test cycles.

How to Diagnose and Troubleshoot

A systematic diagnostic approach is crucial for P1167:

1. Retrieve Freeze Frame Data: Connect an OBD-II scanner and retrieve all stored DTCs and associated freeze frame data. This data captures engine conditions (RPM, engine temperature, throttle position, etc.) at the moment the code was set, providing valuable clues. Pay close attention to the TPS/APP sensor percentage or voltage reading.
2. Visual Inspection:
   • Inspect the throttle body for any physical obstructions, excessive carbon buildup, or binding that might prevent the throttle plate from fully closing. Manually check for smooth, unimpeded operation.
   • Carefully examine the wiring harness and connectors for the TPS/APP sensor for signs of damage, fraying, corrosion, or loose connections. Trace the wiring back to the ECM for any visible issues.
3. OBD-II Live Data Analysis (KOEO & Engine Idling):
   • With the ignition on (Key On Engine Off – KOEO), monitor the live data stream for the TPS/APP sensor voltage (often displayed as a percentage of throttle opening). A healthy closed throttle reading typically ranges from 0.4V to 0.9V (or 0-5%). Note any readings outside this range, or erratic fluctuations.
   • Start the engine and allow it to reach operating temperature. Observe the TPS/APP sensor readings at idle. They should remain stable and within the specified closed-throttle range. Slowly depress and release the accelerator pedal, observing the sensor readings for smooth, consistent voltage changes without any drops or spikes.
4. Digital Multimeter (DMM) Testing of TPS/APP Sensor:
   • Voltage Supply: With KOEO, backprobe the TPS/APP sensor connector to verify the 5-volt reference signal and a solid ground connection. Both should be stable and within specifications.
   • Signal Voltage: Backprobe the TPS/APP sensor signal wire. At closed throttle, measure the voltage. It should align with the manufacturer’s specification (e.g., 0.5V). Slowly open the throttle by hand or with the accelerator pedal and observe the voltage increase. It should smoothly rise to approximately 4.5V-4.9V at wide-open throttle (WOT) without any sudden drops or flat spots, indicating a smooth resistive track. Any interruptions suggest an internal sensor fault.
5. Continuity Test: If wiring damage is suspected, disconnect the ECM and the TPS/APP sensor. Use a DMM to test for continuity between the corresponding pins at both ends of the harness. Also, check for shorts to ground or power.
6. ECM Software/Functionality: If all sensor and wiring integrity checks pass, and the throttle body is mechanically sound, consider checking for Technical Service Bulletins (TSBs) related to P1167 for your specific vehicle make and model. In rare cases, an ECM software update or internal ECM fault might be the root cause.

Recommended Repairs and Solutions

Once the diagnostic process pinpoints the source of the issue, the following repairs are typically performed:

• Replace Throttle Position Sensor (TPS) or Accelerator Pedal Position (APP) Sensor: If DMM testing or live data monitoring confirms the sensor is faulty, exhibiting incorrect voltage, erratic readings, or an open circuit. Ensure proper recalibration or relearn procedure is followed after replacement, if required by the manufacturer.
• Repair or Replace Wiring Harness: If visual inspection or continuity tests reveal damaged, shorted, or open circuits in the TPS/APP sensor wiring, perform precise repairs using appropriate connectors and heat-shrink tubing, or replace the affected section of the harness.
• Clean or Replace Connectors: If corrosion or poor contact is found at the electrical connectors, clean them thoroughly with a specialized electrical contact cleaner. If severe damage is present, replace the affected connector.
• Throttle Body Service: If carbon buildup is impeding the throttle plate’s full closure, clean the throttle body thoroughly using a throttle body cleaner. If mechanical damage or excessive wear is present, leading to binding or incorrect physical positioning, replacement of the throttle body assembly may be necessary.
• ECM Reprogramming or Replacement: As a final resort, if all other components and wiring are verified as functional and within specifications, consider checking for available ECM software updates. If no updates are available and an internal ECM fault is suspected, ECM replacement and programming by a qualified technician may be required.

Mechanic’s Tip: After any repair, clear the DTCs and perform a complete drive cycle that includes varying throttle positions (idle, partial, WOT) and speeds. Use an OBD-II scanner to monitor readiness monitors for completion. This verifies the repair and ensures the ECM can now successfully run its diagnostic tests without the “throttle not depressed” conflict.