Idle Fluctuation, DTC P0505 and P1129 Check IAC Valve

SOURCE:
Honda Service News September 2004

TITLE:
Idle Fluctuation, DTC P0505, P1129? Check the IAC Valve.

APPLIES TO:
2001-03 Odyssey

SERVICE TIP:
A bad IAC valve can cause any or all of these symptoms:

- Fluctuating engine idle

- DTC P0505 (idle control system malfunction)

- DTC P1129 (MAP sensor signal higher than expected)

And if you're still troubleshooting with a PGM Tester, you could also get a bogus DTC 1684 (throttle valve return spring problem). It's bogus because there's no such DTC for these models.

This problem can be very intermittent, so it's really tough to duplicate the symptoms. Fortunately, the presence of these two DTCs are dead giveaways for a bad IAC valve. And even if you find no DTCs, you can suspect the IAC valve if you're getting persistent complaints from your customer of a fluctuating engine idle.

To fix this problem, replace the IAC valve. Refer to S/B 04-007, Idle Fluctuation With DTC P1129, for details.