DTC P15C4 (118): Auto Idle Stop System Malfunction

WARNING: This page is about a different car, the 2011 Honda Insight and 2010 Honda Insight. However, it is still accessible from the selected car via links, so may be relevant.

NOTE:

Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
If the DTC cannot be cleared, do the troubleshooting for DTC U1204(55).
This DTC is stored when the auto idle stop is prohibited due to failure.

Turn the ignition switch to ON (II).
Clear the DTC with the HDS (see DTC CLEAR ).
Check for Pending or Confirmed DTCs with the HDS.
Is DTC U1221 (35) indicated?

YES -Do the troubleshooting for DTC U1221 (35) (see DTC U1221 (35): MOTOR CONTROL MODULE (MCM) LOST COMMUNICATION WITH DC-DC CONVERTER ), then reset the PCM with the HDS (see HDS CLEAR COMMAND ).

NO -go to step 4.
Check the AUTO IDLE STOP DOES NOT OCCUR (BRAKE) in the PGM-FI SYSTEM with the HDS.
Does the screen indicate EXIST?

YES -Go to the brake booster pressure monitoring system's general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ). When the brake booster pressure monitoring system troubleshooting is completed, clear the DTC.

NO -go to step 5.
Check the AUTO IDLE STOP DOES NOT OCCUR (A/C) in the PGM-FI SYSTEM with the HDS.
Does the screen indicate EXIST?

YES -Go to the climate control system's general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ). When the climate control system troubleshooting is completed, clear the DTC.

NO -go to step 6.
Check the IDLE STOP SW in the PGM-FI DATA LIST with the HDS.
Does it indicate OPEN when the brake pedal is pressed and CLOSE when the brake pedal is released?

YES -The system is OK at this time. go to step 20.

NO -
- If CLOSE stays on, go to step 7.
- If OPEN stays on, go to step 10.
Turn the ignition switch to LOCK (0).
Disconnect the idle stop switch 2P connector.
Check the IDLE STOP SW in the PGM-FI DATA LIST with the HDS.
Does the screen indicate OPEN?

YES -Replace the idle stop switch (see IDLE STOP SWITCH REPLACEMENT ), then go to step 19.

NO -Repair a short to power in the wire between the idle stop switch 2P connector and the PCM (A13), then go to step 19.
Turn the ignition switch to LOCK (0).
Disconnect the idle stop switch 2P connector.
Connect idle stop switch 2P connector terminals No. 1 and No. 2 with a jumper wire.

Fig 1: Connecting Idle Stop Switch 2P Connector Terminals 1 And 2 With Jumper Wire
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Turn the ignition switch to ON (II).
Check the IDLE STOP SW in the PGM-FI DATA LIST with the HDS.
Does the screen indicate CLOSE?

YES -Replace the idle stop switch (see IDLE STOP SWITCH REPLACEMENT ), then go to step 19.

NO -go to step 15.
Turn the ignition switch to LOCK (0).
Disconnect the jumper wire from the idle stop switch 2P connector.
Turn the ignition switch to ON (II).
Measure the voltage between body ground and idle stop switch 2P connector terminal No. 2.

Fig 2: Measuring Voltage Between Body Ground And Idle Stop Switch 2P Connector Terminal 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?

YES -Repair an open in the wire between the idle stop switch 2P connector and the PCM (A13), then go to step 19.

NO -Repair an open in the wire between the No. 12 IMA (10 A) fuse and the idle stop switch 2P connector, then go to step 19.
Turn the ignition switch to LOCK (0).
Reconnect all connectors.
Turn the ignition switch to ON (II).
Clear the DTC with the HDS (see DTC CLEAR ).
Check for Pending or Confirmed DTCs with the HDS.
Is DTC P15C4 (118) indicated?

YES -Check for poor connections or loose terminals at the PCM and the idle stop switch. Also check for brake system and climate control system DTCs, then go to step 1.

NO -Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.