Check for continuity between ECM/PCM connector terminal A21 and body ground. ECM/PCM CONNECTOR A (31P) Wire side of female terminals Is there continuity? YES - Repair short in the wire between the ECM/PCM (A21) and the MAP sensor. NO - Substitute a known-good ECM/PCM and recheck, refer to the '01 Civic Shop Manual on this CD (see page 11-313). If symptom/indication goes away, replace the original ECM/PCM. Measure voltage between body ground and ECM/PCM connector terminal A20. ECM/PCM CONNECTOR A (31P) Wire side of female terminals Is there about 5 V? YES - Substitute a known-good ECM/PCM and recheck, refer to the '01 Civic Shop Manual on this CD (see page 11-313). If symptom/indication goes away, replace the original ECM/PCM. NO - Go to step 64.

Turn the ignition switch OFF. Disconnect the 3P connector from each of these sensors, one at a time and measure voltage between body ground and ECM/PCM connector terminal A20 with the ignition switch ON (II). Exhaust gas recirculation (EGR) valve position sensor Knock sensor Throttle position (TP) sensor ECM/PCM CONNECTOR A (31P) Wire side of female terminals Is there about 5 V? YES - Replace the sensor that restored about 5 V when disconnected. NO - Go to step 66. Turn the ignition switch OFF. Disconnect the 3P connectors from the following sensors. Exhaust gas recirculation (EGR) valve position sensor Knock sensor Throttle position (TP) sensor Disconnect ECM/PCM connector A (31P).