P1422

What Does Code P1422 Mean?

DTC P1422 signifies a detected malfunction within a circuit associated with an EGI Temperature Sensor. While the term “EGI” (Electronic Gasoline Injection) can be broad, in the context of a P14xx series code, this specific temperature sensor is most commonly associated with the Secondary Air Injection (SAI) System or an exhaust gas temperature monitoring component crucial for emissions control. The Engine Control Module (ECM), also known as the Powertrain Control Module (PCM), monitors the electrical signal from this sensor to ensure its operational integrity and the proper functioning of the subsystem it monitors. The sensor is typically a thermistor, which changes its electrical resistance in response to temperature variations. The ECM provides a reference voltage (typically 5V) to the sensor and interprets the resulting voltage drop across the sensor as a temperature reading.

Code P1422 is triggered when the ECM detects an implausible voltage signal from the EGI Temperature Sensor. This could mean the voltage is continuously too high (indicating an open circuit or short to voltage), too low (indicating a short to ground or an open circuit on the reference side), or remains static when temperature changes are expected. The ECM uses this temperature input for various calculations, such as determining the appropriate time and duration for secondary air injection, monitoring catalyst efficiency, or preventing damage to emissions components. When the sensor fails, the ECM cannot accurately assess the temperature condition of the monitored system, leading to the illumination of the Malfunction Indicator Lamp (MIL) and potentially compromising emissions control.

Common Symptoms

• Malfunction Indicator Lamp (MIL) illumination: The “Check Engine” light will be illuminated on the dashboard.
• Failed emissions test: The vehicle may fail required emissions inspections due to the compromised emissions control system.
• Reduced fuel economy: While not always a direct symptom, the ECM might enter a less efficient operating mode to protect the engine or catalyst, potentially impacting fuel efficiency.
• Rough idle or poor engine performance: Less common as a direct result of this specific sensor, but possible if the related system (e.g., SAI) is critical for specific engine operating conditions.
• Increased exhaust emissions: Due to the impaired secondary air injection system or inaccurate temperature monitoring, the vehicle’s exhaust may contain higher levels of pollutants.

What Causes the Code P1422?

• Faulty EGI Temperature Sensor: The most common cause is an internal failure of the sensor itself, such as an open circuit, short circuit, or a degradation in the thermistor’s ability to accurately measure temperature.
• Wiring harness issues: Damage to the sensor’s wiring, including chafing, corrosion, cuts, or open circuits in the signal, reference voltage, or ground wires between the sensor and the ECM.
• Corroded or loose electrical connectors: Poor electrical contact at the sensor connector or the ECM connector due to corrosion, bent pins, or improper seating.
• Short to voltage or ground: The sensor’s signal wire may be shorted to a constant voltage source or to chassis ground, causing an out-of-range reading.
• ECM/PCM malfunction: While rare, an internal fault within the ECM’s input circuit for the EGI Temperature Sensor can lead to misinterpretation of the sensor’s signal.

How to Diagnose and Troubleshoot

Diagnosing P1422 requires a methodical approach, utilizing an OBD-II scanner, a digital multimeter (DMM), and visual inspection.

1. Retrieve Freeze Frame Data: Connect an OBD-II scanner and record the freeze frame data associated with P1422. This data provides crucial information about engine operating conditions (engine speed, load, temperature, etc.) at the time the code was set, which can help replicate the fault.
2. Visual Inspection:
   • Locate the EGI Temperature Sensor, typically found within the exhaust manifold for the secondary air injection system or near the catalytic converter.
   • Inspect the sensor and its electrical connector for any obvious signs of damage, corrosion, melting, or loose connections.
   • Trace the wiring harness from the sensor back to the ECM, looking for any signs of chafing, cuts, pinches, or other damage that could cause a short or open circuit. Pay close attention to areas where the harness passes near hot exhaust components or sharp edges.
3. Check Sensor Live Data with OBD-II Scanner:
   • With the ignition ON and engine OFF, observe the EGI Temperature Sensor reading on the live data stream. An extremely low reading (e.g., -40°C) often indicates an open circuit, while an extremely high reading (e.g., 150°C+ when cold) can indicate a short to voltage.
   • Start the engine and allow it to warm up. Monitor the EGI Temperature Sensor reading. It should change smoothly and logically as the exhaust system heats up. If the reading remains static or jumps erratically, the sensor or its circuit is suspect.
4. Digital Multimeter (DMM) Tests:
   • Voltage Reference Check (Ignition ON, Engine OFF, Sensor Disconnected): Disconnect the EGI Temperature Sensor’s electrical connector. With the ignition ON, measure the voltage between the reference voltage wire (typically 5V) and the ground wire at the harness side of the connector. You should see approximately 5V. If not, investigate the wiring back to the ECM or the ECM itself. Also, confirm good ground continuity on the ground wire.
   • Sensor Resistance Test (Sensor Disconnected): Measure the resistance across the two terminals of the EGI Temperature Sensor itself. Compare this reading to manufacturer specifications for the ambient temperature. As a thermistor, its resistance should change predictably with temperature (e.g., resistance decreases as temperature increases for an NTC type). You can gently apply a heat gun to the sensor (away from the connector) and observe if the resistance changes smoothly.
   • Continuity Check (ECM Disconnected): With the battery disconnected and the ECM connector unplugged, perform continuity checks on the signal, reference, and ground wires between the sensor connector and the ECM connector. Look for any open circuits or shorts to ground/power in the harness.
   • Signal Voltage Backprobe (Engine Running, Sensor Connected): Carefully backprobe the signal wire at the sensor connector (or closer to the ECM) with the sensor connected and the engine running. Monitor the voltage as the engine warms up. This voltage should fluctuate within the manufacturer’s specified range, indicating the sensor is actively sending a signal to the ECM.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs and solutions are typically recommended:

• Replace the EGI Temperature Sensor: If the sensor itself fails the resistance tests, shows implausible live data readings, or does not respond to temperature changes, replacement is the most common solution. Ensure the correct OEM-equivalent part is used, as sensor characteristics can vary significantly.
• Repair or Replace Wiring Harness: If damaged or corroded wiring is identified during visual inspection or continuity tests, the affected section of the wiring harness should be repaired using appropriate automotive-grade connectors, solder, and heat-shrink tubing. For extensive damage, harness replacement may be necessary.
• Clean or Replace Electrical Connectors: Address any corrosion or damage found on the electrical connectors. Use specialized contact cleaner for corrosion and replace connectors that are severely damaged or have bent/broken pins. Ensure a tight, secure connection after cleaning or replacement.
• Address Exhaust System Leaks: While not a direct cause of sensor failure, a significant exhaust leak upstream of the EGI temperature sensor could cause it to read inaccurately low temperatures, potentially triggering the code if the ECM expects higher temperatures. Repair any identified exhaust leaks.
• ECM/PCM Diagnosis and Replacement: Only consider ECM replacement as a last resort, after meticulously ruling out all other possibilities related to the sensor, wiring, and connectors. ECM failures are rare and require specialized diagnostic tools and expertise to confirm. If an ECM is replaced, it will typically require programming to the vehicle.

After performing any repairs, clear the DTCs with an OBD-II scanner and perform a drive cycle under varying conditions to confirm that the P1422 code does not reappear and that the EGI Temperature Sensor is reporting accurate data to the ECM.