P256E: Engine Idle Speed Selector Sensor/Switch Circuit Intermittent/Erratic
The P256E code indicates an intermittent or erratic signal from the engine idle speed selector sensor or switch circuit. This sensor monitors the position of the idle speed selector (often part of the throttle body or idle air control system) and sends a voltage signal to the PCM. An intermittent/erratic signal suggests a loose connection, damaged wiring, or a failing sensor, causing the PCM to receive inconsistent data and potentially affect idle control.
01. Most Common Causes
- Faulty idle speed selector sensor
- Damaged or corroded wiring/connectors in the sensor circuit
- Loose electrical connection at the sensor or PCM
- Intermittent short or open in the circuit
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Rough or unstable idle
- Engine stalling at idle
- Poor throttle response
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the idle speed selector sensor and its wiring harness for damage, corrosion, or loose connections.
Step 3: Test the sensor's voltage and resistance per manufacturer specifications using a multimeter.
Step 4: Check for intermittent signal by wiggling the wiring harness while monitoring the sensor signal with a scan tool or oscilloscope.
Step 5: If necessary, replace the sensor and clear the code, then test drive to verify repair.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it can cause stalling or erratic idle, which may lead to unsafe driving conditions. Have the issue diagnosed and repaired promptly.
How much does it cost to fix?▼
The typical repair cost ranges from $50 to $150, including parts and labor. The sensor itself is usually inexpensive, but diagnostic time may add to the cost.