432 Section 4 Computer Control Technology Copyright Goodheart-Willcox Co., Inc. Computer System Sensor and Actuator Diagnosis Condition Possible Causes Correction Poor performance and gas mileage. 1. Faulty coolant temperature sensor. 2. Faulty air temperature sensor. 3. Maladjusted or defective throttle position sensor. 4. Faulty EGR position sensor. 5. Defective or contaminated oxygen sensor. 6. Maladjusted or faulty crankshaft position sensor. 7. Faulty manifold absolute pressure sensor. 8. Bad mass airflow sensor. 9. Bad fuel injectors. Test components and related circuitry. Service or replace as necessary. Erratic acceleration. 1. Faulty EGR position sensor. Test sensor and related circuitry. Service as necessary. Pinging. 1. Bad coolant temperature sensor. 2. Maladjusted or defective throttle position sensor. 3. Defective EGR position sensor. 4. Faulty manifold absolute pressure sensor. 5. Bad mass airflow sensor. 6. Faulty knock sensor. Test sensors and related circuitry. Service or replace as necessary. Surging at highway speeds. 1. Bad coolant temperature sensor. 2. Maladjusted or defective throttle position sensor. 3. Defective EGR position sensor. 4. Faulty manifold absolute pressure sensor. 5. Bad mass airflow sensor. Test sensors and related circuitry. Service or replace as necessary. Backfiring. 1. Maladjusted or defective throttle position sensor. 2. Faulty manifold absolute pressure sensor. 3. Bad mass airflow sensor. Test sensors and related circuitry. Service or replace as necessary. Black exhaust smoke. 1. Bad coolant temperature sensor. 2. Faulty intake air temperature sensor. 3. Faulty oxygen sensor. 4. Faulty manifold absolute pressure sensor. 5. Bad mass airflow sensor. 6. Bad fuel injectors. Test components and related circuitry. Service or replace as necessary. No torque converter lockup. 1. Maladjusted or defective throttle position sensor. 2. Faulty EGR position sensor. 3. Faulty manifold absolute pressure sensor. 4. Bad mass airflow sensor. 5. Faulty torque converter lockup solenoid. 6. Faulty or maladjusted brake light switch. Test components and related circuitry. Service or replace as necessary. Run on. 1. Defective idle speed motor. Test motor and related circuitry. Service or replace as necessary.