Diagnostic Trouble Codes (DTC)

The airbag control module has detected a fault in the passenger-side frontal airbag deployment circuit (Stage 1). This indicates a wiring, connector, or airbag squib issue that could prevent proper deployment in a collision.

The driver seat position sensor circuit has a fault. This sensor is used by the airbag system to determine seat position for optimal airbag deployment force.

The airbag control module has lost communication with the front impact sensor #1, typically located behind the bumper or in the front crush zone. This sensor provides critical crash deceleration data.

The airbag control module has lost communication with the front impact sensor #2, the companion sensor to B0100. Both sensors must be operational for the SRS system to accurately determine crash severity and deploy airbags appropriately.

The left front wheel speed sensor circuit has a fault. The ABS module uses wheel speed sensors to detect wheel lockup and modulate brake pressure accordingly.

The right front wheel speed sensor circuit has a fault. Same system as C0035 but on the opposite side.

The left rear wheel speed sensor circuit has a fault. Rear wheel speed sensors are particularly susceptible to damage from road debris and corrosion.

The right rear wheel speed sensor circuit has a fault. Completes the set of four wheel speed sensor codes (C0035, C0040, C0045, C0050).

The ECM has detected an issue with the intake camshaft position actuator circuit on Bank 1. This actuator controls variable valve timing (VVT) by adjusting camshaft position relative to crankshaft position to optimize engine performance and emissions.

The crankshaft and camshaft position sensors are reporting timing values that do not correlate within the expected range. This indicates the engine's mechanical timing may be off, or a sensor is providing inaccurate data.

The heater circuit in the upstream oxygen sensor (Bank 1, Sensor 1) has malfunctioned. The heater element brings the O2 sensor to operating temperature quickly after a cold start, enabling the ECM to enter closed-loop fuel control sooner.

The Mass Air Flow (MAF) sensor is reporting values outside the expected range for the current engine operating conditions. The MAF sensor measures the volume and density of air entering the engine, which the ECM uses to calculate fuel injection timing and quantity.

The ECM has detected a voltage signal from throttle position sensor A that is outside the expected range. The TPS tells the ECM how far the throttle blade is open so it can calculate proper fuel delivery and ignition timing.

The ECM has detected that the throttle position sensor A output does not correlate with expected values based on other engine parameters like MAP sensor, MAF sensor, and engine RPM. The signal may be erratic or inconsistent.

The ECM is reading a voltage from throttle position sensor A that is below the minimum threshold (typically below 0.2V). This usually indicates an open circuit, ground short, or complete sensor failure.

The engine coolant has not reached the expected temperature within a specified time after starting. The ECM monitors coolant temperature to manage fuel enrichment, emissions controls, and transmission shift strategy.

The ECM has detected a malfunction in the heater circuit of the upstream oxygen sensor on Bank 1. The heater brings the O2 sensor to operating temperature quickly, enabling closed-loop fuel control sooner after cold start.

The ECM has detected that the air-fuel mixture on Bank 1 is running too lean — meaning there is too much air or not enough fuel. The long-term fuel trim has exceeded the positive correction threshold.

Identical to P0171 but on Bank 2. The air-fuel mixture is running too lean on the second bank of cylinders. When both P0171 and P0174 are present simultaneously, the cause is typically a shared component (MAF sensor, fuel pressure, large vacuum leak).

The ECM has detected a fault in the secondary throttle position sensor (TPS B), which provides a redundant signal to verify the primary TPS A reading. Modern electronic throttle systems require both sensors to agree for safe operation.

The ECM is reading an abnormally low voltage from throttle position sensor B. Since TPS B is the redundancy check for TPS A, a low signal here will cause the ECM to enter a protective reduced power mode.

The ECM has detected that the turbocharger or supercharger is not producing the expected amount of boost pressure. The actual boost is significantly below the target value commanded by the ECM.

The ECM has detected random or multiple cylinder misfires. Unlike single-cylinder codes (P0301–P0308), P0300 indicates the misfire pattern is not isolated to one cylinder, suggesting a systemic cause affecting the entire engine.

A misfire has been detected specifically in Cylinder 1. The ECM monitors crankshaft speed variations to identify which cylinder is not producing its expected power contribution.

A misfire has been detected specifically in Cylinder 2. Same detection method as P0301 — crankshaft speed variation analysis isolates the misfiring cylinder.

A misfire has been detected specifically in Cylinder 3.

A misfire has been detected specifically in Cylinder 4.

A misfire has been detected specifically in Cylinder 5.

A misfire has been detected specifically in Cylinder 6.

A misfire has been detected specifically in Cylinder 7.

A misfire has been detected specifically in Cylinder 8.

The knock sensor on Bank 1 is not providing a valid signal. The knock sensor detects engine detonation (pre-ignition) and allows the ECM to retard timing to prevent engine damage.

The crankshaft position sensor (CKP) circuit is not providing a signal. The CKP sensor is critical — it tells the ECM the exact rotational position and speed of the crankshaft, which is essential for ignition timing and fuel injection.

The camshaft position sensor (CMP) circuit on Bank 1 is not providing a valid signal. The CMP sensor works with the CKP sensor to determine which cylinder is on its compression stroke for sequential fuel injection.

The EGR (Exhaust Gas Recirculation) system is not flowing enough exhaust gas back into the intake. The EGR system reduces combustion temperatures to lower NOx emissions.

The catalytic converter on Bank 1 is not operating at expected efficiency. The ECM compares upstream and downstream O2 sensor signals — when they mirror each other too closely, the catalyst is no longer converting pollutants effectively.

Same as P0420 but on Bank 2. The catalytic converter on the second bank is below the efficiency threshold. On V-configuration engines, each bank has its own converter.

A general malfunction has been detected in the EVAP (Evaporative Emission Control) system. This system captures fuel vapors from the tank and routes them to the engine for combustion rather than releasing them into the atmosphere.

The EVAP system purge flow is not within the expected range. The purge valve should allow a controlled amount of fuel vapor to flow from the charcoal canister to the intake manifold.

A small leak (less than 0.040" diameter) has been detected in the EVAP system. The ECM performs a leak test by sealing the system and monitoring pressure decay.

The EVAP purge control valve circuit has an electrical fault. The ECM cannot properly command the purge valve open or closed.

The EVAP vent control circuit has malfunctioned. The vent valve controls airflow into the charcoal canister and is essential for the system's leak detection self-test.

The EVAP vent valve/solenoid circuit has an electrical malfunction. This is the circuit-specific version of P0446.

A large leak has been detected in the EVAP system. This is typically a gross leak — something obvious like a missing gas cap or a disconnected hose.

A very small leak (less than 0.020" diameter) has been detected in the EVAP system. These micro-leaks are the hardest to find and often require smoke testing equipment.

The EVAP system is detecting purge flow when none is commanded. Fuel vapors are being drawn into the engine at the wrong time.

The EVAP system is detecting lower purge flow than expected when the purge valve is commanded open.

The vehicle speed sensor (VSS) is not providing a signal to the ECM. The VSS is critical for speedometer operation, transmission shift strategy, cruise control, and ABS function.

The engine idle speed is lower than the ECM's expected target RPM. The ECM is attempting to raise idle speed but cannot achieve the target.

The engine idle speed is higher than the ECM's expected target RPM. The ECM is attempting to lower idle speed but cannot achieve the target.

The ECM has detected that the system voltage (battery/charging voltage) is below the expected threshold. Normal operating voltage is 13.5–14.5V with the engine running.

This is an informational code indicating that the Transmission Control Module (TCM) has detected a fault and stored its own diagnostic code. P0700 itself does not identify the specific transmission problem — a transmission-specific scan is required to read the TCM codes.

The input/turbine speed sensor circuit is not providing a valid signal. This sensor measures the rotational speed of the transmission input shaft (torque converter turbine), which the TCM uses to calculate gear ratios and shift points.

The TCM or ECM has detected a malfunction in the transmission output speed sensor circuit. This sensor measures how fast the transmission output shaft is turning, which is critical for shift timing, torque converter lockup, and speedometer accuracy.

The TCM has detected that the actual gear ratio does not match the expected gear ratio. This indicates the transmission is not achieving the correct gear — it may be slipping, stuck between gears, or has an internal mechanical failure.

The torque converter clutch (TCC) is not engaging or is slipping when commanded. The TCC locks the torque converter at highway speeds to eliminate slippage and improve fuel economy.

Shift solenoid A is not performing as expected or is stuck in the off position. Shift solenoids are electro-hydraulic valves that direct transmission fluid to engage specific gear sets.

The TCM has detected a problem with pressure control solenoid B inside the transmission valve body. This solenoid regulates hydraulic pressure for specific gear ranges, and its failure can cause harsh or delayed shifts.

The TCM has detected that the transmission line pressure is below the minimum acceptable threshold. Adequate fluid pressure is essential for clutch pack engagement, band application, and torque converter operation.

The TCM has detected insufficient hydraulic pressure in the overdrive brake clutch circuit. This clutch is responsible for holding components in the overdrive gear range, and low pressure causes it to slip.

The hybrid battery management system has determined that the high-voltage battery pack has degraded beyond acceptable limits. Individual cell voltage imbalances or overall capacity loss has exceeded the manufacturer's threshold for safe and efficient operation.

The hybrid control module has detected that the high-voltage battery system has lost electrical isolation from the vehicle chassis. This is a serious safety fault indicating that high voltage may be present on the vehicle body.

The intake air flow system is not performing within the expected range. This is a manufacturer-specific code (common on GM vehicles) that indicates the actual airflow does not match the ECM's calculated expected airflow.

The TCM has detected a mechanical fault within the transmission that does not correspond to a specific electrical circuit or solenoid failure. This is a general mechanical failure code often seen in VW/Audi DSG and modern automated transmissions.

The TCM has detected that clutch B in the transmission is not engaging properly or is stuck in the released position. This is typically seen in modern multi-clutch automatic and DCT transmissions where precise clutch engagement is electronically controlled.

The ECM has determined that the diesel particulate filter (DPF) on Bank 1 is not filtering soot efficiently enough to meet emissions standards. The DPF may be clogged, damaged, or the regeneration process is not completing successfully.

The post-catalyst fuel trim on Bank 1 is indicating a lean condition. The downstream O2 sensor is detecting that the exhaust leaving the catalytic converter has too much oxygen.

The post-catalyst fuel trim on Bank 1 is indicating a rich condition. The downstream O2 sensor is detecting excess hydrocarbons in the exhaust after the catalytic converter.

The ECM has detected that the selective catalytic reduction (SCR) system is not converting NOx emissions efficiently enough. The SCR uses diesel exhaust fluid (DEF/AdBlue) to neutralize nitrogen oxides in the exhaust.

The ECM has detected that the voltage signals from throttle position sensors A and B do not correlate properly. These dual sensors are designed to mirror each other for safety verification, and a mismatch triggers immediate protective action.

The two throttle/pedal position sensor signals do not agree with each other. Modern drive-by-wire systems use redundant sensors for safety — when they disagree, the ECM limits engine power as a precaution.

The downstream O2 sensor on Bank 2 is stuck reading lean. The signal voltage remains below the expected switching threshold, indicating the sensor is not oscillating normally.

The ECM has detected that soot accumulation in the diesel particulate filter has exceeded the threshold where passive or active regeneration can clear it. The DPF is at risk of becoming permanently damaged if not addressed.

The battery management system has logged a general malfunction in the high-voltage battery pack. This is often a parent code that accompanies more specific sub-codes identifying the exact failure within the battery system.

Communication has been lost between the body control module or other module and the Engine Control Module (ECM) / Powertrain Control Module (PCM) on the CAN bus network. This is a network communication fault, not an engine fault.

Communication has been lost with the Transmission Control Module (TCM) on the CAN bus network. The ECM and TCM must communicate for proper shift strategy and torque management.