P1498
EGR Valve Position Sensor Circuit High Voltage
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The P1498 code is a Honda-specific code indicating that the EGR valve position sensor is reporting a voltage higher than the expected range. The EGR valve has an integrated position sensor that tells the ECM exactly how far the valve is open. When this sensor outputs excessively high voltage, the ECM cannot accurately control EGR flow and stores this code.
This code often appears alongside P1491 (EGR Valve Insufficient Lift) because they both relate to the same EGR valve assembly. A useful diagnostic trick is to unplug the EGR valve connector and check if the code changes to P1498 after 30 seconds with a scan tool — if it does, this confirms the wiring, sensor, and ECM are functioning correctly, and the issue is mechanical (carbon buildup or valve sticking).
The EGR position sensor is not sold separately on most Honda models — it's integrated into the EGR valve assembly. If the sensor itself is faulty, the entire EGR valve must be replaced. However, before buying a new valve, try cleaning the existing one thoroughly. Carbon deposits can physically push the sensor element out of its normal range. Removing the EGR valve, cleaning it with carburetor cleaner, and clearing the code resolves many cases of P1498.
Severity
Symptoms
- •Check Engine light illuminated
- •Rough idle or slight engine hesitation
- •Marginally reduced fuel efficiency
- •Failed emissions inspection
- •Possible light engine knock under load
- •Engine may idle slightly higher or lower than normal
Likely Causes
The position sensor integrated into the EGR valve can fail and output abnormally high voltage, making the ECM think the valve is stuck open.
Wiring between the EGR valve position sensor and ECM can corrode or short to the power supply line, causing high voltage readings.
Heavy carbon buildup on the EGR valve can physically interfere with the position sensor, pushing it out of range.
An issue with the ECM's 5V reference circuit supplying the sensor can cause abnormally high readings, though this is uncommon.
Estimated Cost
Professional Repair
Includes parts + labor
Common Fixes
- Replace the EGR valve assembly (includes position sensor)
- Clean carbon deposits from the EGR valve
- Repair or replace corroded wiring and connectors in the sensor circuit
- Verify ECM reference voltage at sensor connector