Engine Speed Input Circuit Intermittent
The P0728 code indicates an intermittent fault in the engine speed input circuit, which is typically monitored by the crankshaft position sensor or engine speed sensor. This circuit provides critical data to the PCM for ignition timing, fuel injection, and transmission control. An intermittent signal can cause erratic engine behavior and may lead to stalling or no-start conditions.
01. Most Common Causes
- Faulty crankshaft position sensor
- Damaged or corroded wiring/connectors in the sensor circuit
- Intermittent short or open in the circuit
- Loose or damaged reluctor ring on the crankshaft
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine misfire or rough idle
- Intermittent stalling or difficulty starting
- Reduced engine performance or hesitation
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data to identify conditions when the fault occurred.
Step 2: Visually inspect the crankshaft position sensor and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's resistance and AC voltage output while cranking the engine using a multimeter.
Step 4: Check the reluctor ring for damage or debris that could cause intermittent signal loss.
Step 5: If wiring and sensor are okay, test the PCM input circuit for continuity and shorts.
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 sudden stalling or loss of power, leading to unsafe driving conditions.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a new crankshaft position sensor, plus labor if installed by a mechanic.