P1123 LAND-ROVER Possible Causes
- Faulty Accelerator Pedal Position (APP) Sensor
- APP Sensor Wiring Harness Open or Shorted
- Poor Electrical Connection in APP Sensor Circuit
How to Fix P1123 LAND-ROVER Code?
Start by checking the “Possible Causes” listed above. Visually inspect the corresponding wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
Check Engine Light On (or Service Engine Soon Warning Light)
No Throttle Response
P1123 LAND-ROVER Meaning
The Accelerator Pedal Position (APP) sensor is located in a plastic housing integrated with the accelerator pedal. The housing is injection molded and provides a mounting location for the APP sensor. The sensor is externally mounted on the housing and is secured with two Torx screws. The external body of the sensor has a six-pin connector that accepts a connector from the vehicle’s wiring harness.
The sensor has a lug that protrudes into the housing and provides the pivot point for the pedal mechanism. The lug has a slot that allows a pin, which is attached to the sensor’s potentiometers, to rotate approximately 90°, corresponding to the pedal movement. The pedal is connected via a linkage to a drum, which engages with the sensor pin, converting the linear motion of the pedal into rotational motion of the drum. The drum is connected to two steel cables. The cables are attached to two tension springs that are secured at the opposite end of the housing. The springs provide a “feel” to the pedal movement and require driver effort similar to a cable-operated throttle. A detent mechanism is located at the front end of the housing and is actuated by a ball located on the drum. At nearly maximum accelerator pedal movement, the ball contacts the detent mechanism. A spring in the mechanism is compressed and gives the driver the sensation of pressing a “kickdown” switch when full pedal travel is reached.
The APP sensor has two potentiometer tracks, each receiving a 5V input voltage from the ECM. Track 1 provides an output of 0.5V with the pedal at rest and 2.0V at 100% full throttle. Track 2 provides an output of 0.5V with the pedal at rest and 4.5V at 100% full throttle. The signals from both tracks are used by the ECM to determine fuel supply for engine operation and also by the ECM and EAT ECU to initiate a kickdown request for the automatic transmission.
The ECM monitors the outputs from each of the potentiometer tracks and can determine the position, rate of change, and direction of the accelerator pedal movement. The “throttle closed” position signal is used by the ECM to initiate idle control and also to interrupt fuel cut-off.