Check Engine Light Repair and Diagnostic Help
The mass air flow (MAF) sensor is an air flow meter that measures the amount of air entering the engine. The powertrain control module (PCM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates deceleration or idle.Read more: Code P0101 or P0102 Mass Air flow Sensor
The powertrain control module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals, without oxygen sensor (O2S) input.Read more: Code P0171 Fuel Trim Error
During cranking, the ignition control (IC) module monitors the 7X crankshaft position sensor signal. Once the IC module determines spark synchronization, 3X reference signals are sent to the powertrain control module (PCM). The PCM will command all six injectors on for one priming shot of fuel in all cylinders.Read more: Code P0341 Cam Position Sensor
To control emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx), a three-way catalytic converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx, converting the NOx to nitrogen.Read more: Code P0420 Catalytic Converter Failure
The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The powertrain control module (PCM) supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit.Read more: Coolant Temperature Sensor Code P0117 Or P0118
The powertrain control module (PCM) tests the exhaust gas recirculation (EGR) system during deceleration by momentarily commanding the EGR valve to open while monitoring the manifold absolute pressure (MAP) sensor signal. When the EGR valve is opened, the PCM should see a proportional increase in MAP.
P0506 - P0507
The Electronic Throttle Control (ETC) System uses various inputs from the powertrain control module (PCM). This system uses the inputs to control the idle speed through serial data circuits to the throttle actuator control (TAC) module.
The powertrain control module (PCM) uses information from the ignition control (IC) module and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring the variations in the crankshaft rotation speed for each cylinder the PCM is able to detect individual misfire events.Read more: Engine Misfire Code P0300 - P0308
P0440 - P0455
The control module tests the evaporative emission (EVAP) system for a large leak. The control module monitors the fuel tank pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge valve OPEN and the EVAP vent valve CLOSED .
P0506 - P0507
The idle air control (IAC) valve is located in the throttle body of the SFI systems. The IAC consists of a movable pintle, driven by a gear attached to an electric motor called a stepper motor. The IAC valve motor is a two phase bi-polar permanent magnet stepper motor that is capable of highly accurate rotation, or movement, every time the polarity of a winding is changed.
The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The powertrain control module (PCM) applies 5 volts through a pull up resistor. When the intake air is cold, the sensor resistance is high and the PCM will monitor a high signal voltage on the IAT sensor signal circuit.Read more: Intake Air Temperature Sensor (IAT) Code P0112 Or P0113
The powertrain control module (PCM) contains integrated knock sensor (KS) diagnostic circuitry. The KS produces an AC voltage at all engine speeds and loads. The PCM then adjusts spark timing based on the amplitude and frequency of the KS signal.Read more: Knock Sensor Codes P0325 and P0327
P0036 - P0056
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature.
The powertrain control module (PCM) supplies a bias voltage of about 450 mV between the heated oxygen sensor (HO2S) high signal circuit and the HO2S low reference circuit. When measured with a 10 mega ohm digital voltmeter, this may display as low as 350 mV. The oxygen sensor signal varies from about 800 mV when the exhaust is rich, to about 50 mV when the exhaust is lean.Read more: Oxygen Sensor Code P0130 - P0141
The manifold absolute pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits:Read more: P0108 MAP Sensor Description and Repair
An engine coolant temperature (ECT) sensor monitors the temperature of the coolant. This input is used by the powertrain control module (PCM) for engine control and as an enabling criteria for some diagnostics.Read more: P0128 Coolant Temp Below Themostat Threshold
The throttle position (TP) sensor is used by the powertrain control module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with three circuits: a 5-volt reference, a low reference, and a signal. The PCM provides the TP sensor with a 5-volt reference circuit and a low reference circuit.Read more: Throttle Position Sensor Code P0121, P0122 and P0123