P0113: INTAKE AIR TEMPERATURE (IAT) SENSOR HIGH VOLTAGE INPUT
Turn ignition on. Check IAT sensor using scan tool. If -4°F (-20°C) or less is indicated, go to next step. If -4°F (-20°C) or less is not indicated, problem is intermittent. Check for poor connections or loose wires at IAT sensor connector and PCM connector. See the L - WIRING DIAGRAMS article.
Disconnect IAT 2-pin connector. Install jumper wire between IAT sensor connector terminals. Using scan tool, check intake air temperature. If -4°F (-20°C) or less is indicated, go to next step. If -4°F(-20°C) or less is not indicated, replace IAT sensor.
Turn ignition off. Connect jumper wire between PCM 16-pin connector "D" terminal D8 and terminal D11. See Fig. 3 . Turn ignition on. Using scan tool, check intake air temperature. If -4°F(-20°C) or less is not indicated, repair open in wiring between IAT sensor and PCM connector "D". See the L - WIRING DIAGRAMS article. If -4°F (-20°C) or less is indicated, substitute a known-good PCM and recheck. If symptom or indication goes away, replace original PCM.
P0118: ENGINE COOLANT TEMPERATURE (ECT) SENSOR HIGH VOLTAGE INPUT
Turn ignition on. Check ECT using scan tool. If -4°F (-20°C) or less is indicated, go to next step. If -4°F (-20°C) or less is not indicated, problem is intermittent. System is okay at this time. Check for poor connections or loose wires at ECT sensor connector and PCM connector. See the L - WIRING DIAGRAMS article.
Disconnect ECT sensor connector. Install jumper wire between ECT harness connector terminals. Check ECT using scan tool. If -4°F (-20°C) or less is indicated, go to next step. If -4°F (-20°C) or less is not indicated, replace ECT sensor.
Turn ignition off. Install jumper wire between PCM 16-pin connector "D" terminal D2 and terminal D11. Turn ignition on. Check ECT using scan tool. If -4°F (-20°C) or less is not indicated, repair open in wire(s) between ECT sensor and PCM connector terminals. See the L - WIRING DIAGRAMS article. If -4°F (-20°C) or less is indicated, substitute a known-good PCM and recheck. If symptom or indication goes away, replace original PCM.
P0401: EGR INSUFFICIENT FLOW (D16Y5)
NOTE: If DTC P1491 is set when DTC P0401 is set, trouble shoot DTC P1491 before trouble shooting DTC P0401.
Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DTCS . Connect SCS service connector. Test drive vehicle and without any electrical load. Decelerate vehicle from 55 MPH for at least 5 seconds. If DTC P0401 is not indicated, problem is intermittent, system is okay at this time. If DTC P0401 is indicated, clean intake manifold EGR port with carburetor cleaner. Clean passage inside EGR valve with carburetor cleaner or replace valve.