A
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Area "A"- accelerator pedal to powertrain control (PCM) module circuit
B
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Area "B"- electronic throttle body to PCM circuit
2
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42-way electrical connector
4
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16-way inline electrical connector
5
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Electronic throttle body
Description
The system consists primarily of two circuits connected to the PCM. The two circuits are the accelerator pedal to PCM and the electronic throttle body to PCM.
Accelerator Pedal
The accelerator pedal contains two sensors that measure the movement of the pedal and output a voltage corresponding to the pedal position.
Electronic Throttle Body
The electronic throttle body is similar to a mechanical throttle body used on a cable accelerator system. Instead of the cable moving the throttle plate open and closed, it uses an internal electrical motor that is driven by the PCM. The electronic throttle body has two sensors that measure the throttle plate position. The sensors output a voltage to the PCM corresponding to the plate position.
When the electronic throttle body motor is not in use, the throttle plate sits slightly open in a default position (not idle position). This position is maintained by two internal springs. One acts upwards and one downwards. Screws on the electronic throttle body will not adjust the idle speed, the idle speed is controlled by the PCM.
PCM
The PCM reads the voltage from the pedal and converts this signal into a driver request. The driver request is realized by opening or closing the throttle body. To do this, the PCM increases or decreases power to the electronic throttle body motor. The PCM then checks the signal from the electronic throttle body throttle position (TP) sensor, to make sure that the requested position has been achieved. The PCM also monitors all the sensors to make sure that the system is functioning as expected. All electronic accelerator control system faults will be detected by the PCM and set a diagnostic trouble code (DTC) which triggers the electronic accelerator control fail message accordingly. For safety reasons, some faults will also reduce the vehicle performance.
Diagnostic Trouble Codes
Description
When a component electrical error is set it means that the PCM is not receiving the expected signal. This means that the concern may lie between the component and the PCM. All wiring and electrical connectors should be checked before a new component is installed. Also note that general vehicle electrical issues can have an effect on other systems. Battery voltage and relay concerns should be rectified first.
Accelerator Pedal Codes
These are the DTCs relating to the pedal circuit. They do not imply necessarily that the accelerator pedal is at fault, but it will in any case relate to area "A" (see system overview).
- P2120 – Accelerator pedal sensor 1 electrical error
- P2122 – Accelerator pedal sensor 1 electrical error short to ground or open circuit
- P2123 – Accelerator pedal sensor 1 electrical error short to battery
- P2125 – Accelerator pedal sensor 2 electrical error
- P2127 – Accelerator pedal sensor 2 electrical error short to ground or open circuit
- P2128 – Accelerator pedal sensor 2 electrical error short to battery
- P2138 – Accelerator pedal sensor 1 & 2 ratio error
Electronic Throttle Body Circuit Codes
These are the DTCs relating to the electronic throttle body circuit. They do not imply necessarily that the electronic throttle body is the concern, but it will in any case relate to area "B" (see system overview).
- P0120 – Throttle position (TP) sensor 1 electrical error
- P0122 – (TP) sensor 1 electrical error short to ground
- P0123 – (TP) sensor 1 electrical error short to battery or line break
- P0220 – (TP) sensor 2 electrical error
- P0222 – (TP) sensor 2 electrical error short to ground or open circuit
- P0223 – (TP) sensor 2 electrical error short to battery
- P2135 – (TP) sensor ratio error
- P2119 – Throttle plate convergence error
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This is when the throttle plate has not moved to the requested position in the required time. This could be caused by the following:
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The electronic throttle body motor is not receiving the necessary voltage. Check the electronic throttle body motor wiring. The PCM is not receiving the correct throttle plate position signal from the electronic throttle body. Check the TP sensor wiring from the PCM to the electronic throttle body including the electrical connectors in area "B" (see system overview).
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There is an obstruction inside the throttle body bore. Remove the air cleaner outlet pipe and check for obstructions.
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There is an obstruction inside the electronic throttle body. Remove the air cleaner outlet pipe and check that the plate moves freely against the springs and returns to a slightly open position. If it does not, install a new electronic throttle body.
- P2176 – Throttle plate adaptation error
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When the ignition is turned off, the throttle body carries out an adaptation cycle and spring check. This can be audible after a short delay (up to 30 seconds) following the ignition key being turned to position 0 and can be visually observed with the air cleaner outlet pipe removed. The throttle plate is moved through a series of positions to check the TP sensor value and relearn the electronic throttle body characteristics. If a concern is detected during this test, P2176 DTC will be set. If there are already any of the other DTCs, the adaptation test could potentially fail. Therefore the other DTCs should be resolved first (e.g. low battery voltage) and a retest can be carried out by clearing the DTCs and keying on and off again. Check the whole area "B" (see system overview) for any concerns and if no concern is found, install a new electronic throttle body.
- P2100 – H bridge error
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A fault has been detected on the circuit connecting the electronic throttle body motor and the PCM. Check for any other non-electronic accelerator control related DTCs and rectify them first. Check area "B" (see system overview) and if no failure is found, install a new PCM.
PCM Related Codes
The PCM continuously monitors all the sensors. It also checks that the monitor is functioning as expected. If there is a fault with the monitor, the following DTCs will be set.
- P2107 – Processor monitoring on the main controller fault.
- P2108 -Analogue to digital converter
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Inferred intake mass air flow lower than expected
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Engine speed monitor ratio error
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Pedal ratio monitor error
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TP sensor ratio monitor error
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Fault in torque generation
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Fault present in engine speed limitation
Multiple sensor faults can make the PCM assume that there is a monitor fault. If other DTCs exist, rectify these first. These DTCs indicate a failure in area "A" or "B" and they are also related to the manifold absolute pressure and temperature (MAPT) sensor and the crankshaft position (CKP) sensor. If no other failures are found, install a new PCM.
Indirect Codes
There are two brake pedal switches located under the brake pedal. Check that both of these are connected and functioning correctly. A brake pedal switch concern will only cause the "EAC FAIL" message to be displayed, it will not lead to a limited performance mode. Follow WDS instructions.
- P0571 – Brake switch error
If the voltage to the accelerator pedal and the electronic throttle body cannot be regulated correctly, the components may not operate as expected. Therefore it is important to detect if there is a concern in the supply voltage
- P0641 – Sensor voltage supply circuit 1 noisy signal
- P0642 – Sensor voltage supply circuit 1 short to ground or open circuit
- P0643 – Sensor voltage supply circuit 1 short to battery
- P0651 – Sensor voltage supply circuit 2 noisy signal
- P0652 – Sensor voltage supply circuit 2 short to ground or open circuit
- P0653 – Sensor voltage supply circuit 2 short to battery
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Check the power supply to the PCM (battery voltage, relays, wiring harness and electrical connectors as well as fuses). If no concern is found, install a new PCM.
- P1712 – Electronic gear shift torque demand is not a plausible signal (ASM only)
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Follow WDS instructions.
NOTE:If the vehicle is in a limited performance mode, a system related DTC and the electronic accelerator control fail light message will illuminate. If there is a performance issue without these items the electronic accelerator control system is running correctly but another issue may exist elsewhere on the vehicle.
Be aware that installing new system related components without these DTCs will not improve the vehicle behavior for general issues such as:
- high fuel consumption
- poor idle quality
- poor or no engine start
Inspection and Verification
- Verify the customer concern.
- Visually inspect for obvious signs of mechanical or electrical damage.
Visual Inspection Chart
