Air/Fuel Mixture: Adjustments

1. Bring the vehicle to normal operating temperature and connect an exhaust analyzer.
2. Check the CO reading. If it is not between 0.5 and 1.5% for a naturally aspirated engine, or 0.9 and 1.6% CO for a turbocharged engine, proceed to step 3. If the readings are within specs, the test is over.
3. If the CO reading is too high, turn the adjusting screw clockwise. If it is too low, turn the adjusting screw counter-clockwise.
4. If the CO reading is higher than 6% it cannot be adjusted by means of the adjusting screw. If this is the case, shut off the engine, disconnect the air mass sensor connector and check the resistance between between pins 3 and 6 of the air mass meter. If the reading is greater than 380 Ohms, turn the adjusting screw until this reading is attained. If this reading cannot be attained, replace the air mass meter.
5. Recheck the CO reading, making sure the vehicle is at normal operating temperature. Turn the adjusting screw until the CO reading is within specifications. If the correct value still cannot be reached, check the air mass meter wiring loom and connectors.
6. If the wiring and connectors are in proper condition and the CO still cannot be adjusted, replace the ECU.