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Code 20 - Electrical Load Detector

  1. Turn ignition off. Remove appropriate fuse for 10 seconds to reset ECU. See ECU RESET FUSE CHART  . Start engine, and turn on headlights with engine at idle. Verify if CHECK ENGINE light is on and if LED is flashing Code 20. If Code 20 is present, go to next step. If Code 20 is not present, problem is intermittent. Check for poor connections and loose wires.
  2. Turn ignition off. Open lid of main fuse panel in engine compartment. Disconnect 3-wire electrical load detector. Turn ignition on. Measure voltage between Black/Yellow (+) and Black (-) wire terminals of harness. If battery voltage is present, go to step 4).
  3. If battery voltage is not present, measure voltage between Black/Yellow wire and ground. If battery voltage is now present, repair open in Black wire between connector and ground. If battery voltage is not present, repair open Black/Yellow wire between fuse No. 14 and connector.
  4. Turn ignition off. Connect ECU Test Harness between ECU and ECU connector. See Figure . Disconnect connector "B" from ECU side only. Connect Green/Red terminal of load detector harness connector to ground. Check for continuity between ECU terminal B19 and ground. See Figure . If continuity does not exist, repair open Green/Red wire between ECU connector terminal B19 and load detector connector.
  5. If continuity exists, disconnect Green/Red terminal of 3-wire connector on Civic models. On all models, reconnect connector "B" to ECU. Turn ignition on. Measure voltage between Green/Red (+) and Black (-) terminals of load detector harness. If 4.5-5 volts is present, go to step 7). If 4.5-5 volts is not present, disconnect connector "B" from main wiring harness, not ECU. Measure voltage between positive terminal B19 and negative terminal A18.
  6. If voltage is now 4.5-5 volts, repair short in Green/Red wire between ECU terminal B19 and load detector connector. If voltage is not 4.5-5 volts, substitute a known good ECU. If correct voltage is now available, replace original ECU.
  7. Reconnect load detector connector. Start engine. Measure voltage between positive terminal B19 and negative terminal A18 under following conditions:
    • Headlight switch in 1st pos. - should be 2.5-3.5 volts.
    • Headlight switch in 2nd pos. - should be 1.5-2.5 volts.
  8. If voltage is not as specified, replace faulty electrical load detector. If voltage is as specified, substitute a known good ECU, and retest. If condition is corrected, replace original ECU.
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