DTC P1491 (D16Y5 CVT) - EGR SYSTEM MALFUNCTION Honda Civic VI

1. Perform PCM reset procedure. See Self Diagnostic section. Connect SCS service connector. Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Drive vehicle for about 10 minutes. Maintain engine speed at 1700-2500 RPM. If DTC P1491 is indicated, go to next step. If DTC P1491 is not indicated, problem is intermittent. System is okay at this time. Check for poor connections or loose wires between EGR valve connector and PCM connectors. See «WIRING DIAGRAMS»(ref-16355) article.
2. Turn ignition off. Disconnect No. 16 vacuum hose from top of EGR valve. See «VACUUM DIAGRAMS»(ref-16356) article. Connect vacuum pump/gauge to hose. Start engine and allow it to idle. If vacuum does not exist, go to next step. If vacuum exists, disconnect EGR solenoid valve 2-pin connector. Recheck No. 16 vacuum hose for vacuum. If vacuum exists, check EGR system hose routing. If hose routing is okay, replace EGR control solenoid valve. If vacuum does not exist, substitute a known good PCM, then recheck. If symptom or indication goes away, replace original PCM.
3. Connect vacuum pump/gauge to EGR valve. With engine at idle, apply 8 in. Hg vacuum to EGR valve. If engine stalls or runs rough, and EGR valve holds vacuum, go to next step. If engine does not stall or run rough, or EGR valve does not hold vacuum, replace EGR valve.
4. Connect vacuum pump/gauge to No. 16 vacuum hose. Start engine and allow it to idle. Using a fused jumper wire, connect battery voltage to EGR control solenoid valve terminal No. 1 (Black/Yellow wire). See «WIRING DIAGRAMS»(ref-16355) article. Observe vacuum gauge and briefly connect battery ground to EGR control solenoid valve terminal No. 2 (Red wire). If there is about 8.0 in. Hg vacuum within one second, go to step 6). If there is not about 8.0 in. Hg vacuum within one second, go to next step.
5. Turn ignition off. Check No. 16 and 10 vacuum hoses for leaks, restrictions or misrouting. See «VACUUM DIAGRAMS»(ref-16356) article. Repair or replace hoses as necessary. If hoses are okay, replace EGR control solenoid valve.
6. Turn ignition off and remove jumper wires. Disconnect EGR solenoid valve 2-pin connector. Disconnect PCM 32-pin connector "A". Check for continuity between PCM 32-pin connector terminal A7 (Red wire) and EGR solenoid valve connector terminal No. 2 (Red wire). If continuity exists, go to next step. If continuity does not exist, repair open in Red wire between PCM and EGR control solenoid valve connector. See «WIRING DIAGRAMS»(ref-16355) article.
7. Check for continuity between ground and EGR control solenoid valve connector terminal No. 2 (Red wire). See «WIRING DIAGRAMS»(ref-16355) article. If continuity does not exist, go to next step. If continuity exists, repair short in Red wire between PCM and EGR control solenoid valve connector. See «WIRING DIAGRAMS»(ref-16355) article.
8. Check for continuity between ground and EGR control solenoid valve harness connector terminal No. 1 (Black wire). If continuity does not exist, repair open in Black wire between EGR control solenoid valve and ground connection located at right side of engine. See «WIRING DIAGRAMS»(ref-16355) article. If continuity exists, substitute a known-good PCM and recheck. If symptom or indication goes away, replace original PCM.

Scheme 35

1. Perform PCM reset procedure. See Self Diagnostic section. Connect SCS Service Connector (07PAZ-001010 0). Start engine and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Drive vehicle for about 10 minutes. Maintain engine speed at 1700-2500 RPM. If DTC P1491 is indicated, go to next step. If DTC P1491 is not indicated, problem is intermittent. System is okay at this time. Check for poor connections or loose wires between EGR valve 6-pin connector and PCM. See «WIRING DIAGRAMS»(ref-16355) article.
2. Start engine and allow it to idle. Measure voltage between EGR valve 6-pin connector terminals No. 4 (Black wire) and No. 6 (Pink wire). (Scheme 35) If battery voltage does not exist, go to next step. If battery voltage exists, substitute a known-good PCM and recheck. If symptom or problem goes away, replace original PCM.
3. Turn ignition off. Disconnect EGR valve 6-pin connector. Using a fused jumper wire, connect battery voltage to EGR valve terminal No. 6 (Pink wire). (Scheme 35) Start engine and allow it to idle. Using a fused jumper wire, connect battery ground to EGR valve terminal No. 4 (Black wire). If engine stalls or runs rough, go to next step. If engine does not stall or run rough, replace EGR valve.
4. Turn ignition off and disconnect jumper wires from EGR valve connector. Disconnect PCM 32-pin connector "A". Check for continuity in Pink wire between PCM connector terminal A7 and EGR valve 6-pin connector terminal No. 6. see scheme 1and (Scheme 35). If continuity exists, go to next step. If continuity does not exist, repair open in Pink wire between PCM and EGR valve harness connector. See «WIRING DIAGRAMS»(ref-16355) article.
5. Check for continuity between ground and EGR valve connector terminal No. 4 (Black wire). (Scheme 35) If continuity does not exist, repair open in Black wire between EGR valve harness connector and ground connection G101 located at thermostat housing. See «WIRING DIAGRAMS»(ref-16355) article. If continuity exists, substitute a known-good PCM and recheck. If symptom or problem goes away, replace original PCM.