4501

What the Code Means

Code 4501 points to a fault in the oxygen sensor (O2 sensor) located ahead of the catalytic converter. The sensor measures the oxygen content in the exhaust and sends that data to the engine control unit to adjust the fuel mixture. As the sensor ages, gets contaminated, or develops wiring problems, the control unit loses reliable information about the mixture, and injection correction goes off.

Symptoms

• check engine light on the instrument cluster;
• increased fuel consumption;
• rough idle;
• failed emissions test at inspection.

Diagnosis and Repair

Step 1. Read the Fault Codes

Pull the fault codes through ISTA and note the current and stored errors related to the oxygen sensor.

Step 2. Check the Wiring and Connector

Inspect the sensor wiring and connector for damage, corrosion, and poor contact — these are among the typical causes for code 4501.

Step 3. Replace the Sensor

If the wiring is sound, replace the oxygen sensor with the OEM part 11787558095.

Step 4. Clear and Verify

After replacement, clear the fault codes and take a test drive to confirm the fault is gone.

Secondary Problems

• a faulty oxygen sensor produces the wrong fuel mixture, which over time damages the catalytic converter — replacing it is the expensive repair;
• increased harmful emissions that keep the car from passing the emissions test.

Don't put off the repair: running the engine on an incorrect mixture raises the risk of destroying the catalytic converter.