Honda PGM-FI Code 29: IACV — Causes & Fix
On Honda motorcycles and scooters, PGM-FI code 29 means the ECM has detected a fault in the IACV (idle air control valve) circuit — the valve that meters air to hold a steady idle.
- Applies to
- Honda motorcycles
- Est. repair cost
- $20 – $160
- Time to fix
- 30–90 minutes
What it means
Typical causes are a carbon-clogged IACV/throttle body, a loose/corroded connector, damaged wiring, or a failed IACV. This is a generic Honda PGM-FI (Programmed Fuel Injection) code, so it applies across Honda FI models — scooters and underbones like the Click, Vario, BeAT, PCX, ADV, and Wave, as well as CB/CBR motorcycles. Honda shows it by blinking the FI/MIL warning light: a long blink counts as ten and a short blink counts as one (e.g. one long + two short = code 12). Clearing the code usually needs Honda’s service-check reset procedure (jumping the DLC service connector, or a scan tool) after the fault is fixed; simply resetting without repair will let the light return.
Symptoms
- FI/MIL light on with code 29
- Unstable idle, idle too high or too low
- Stalling at stops or hard starting
- Idle hunts up and down
How to fix it
- 1
Clean the IACV and throttle body
1. Remove the IACV (or access the idle-air passages). 2. Clean carbon from the valve and throttle bore with throttle-body cleaner. 3. Reassemble and retest idle.
- 2
Inspect the connector and wiring
1. Reseat the IACV connector and check for corrosion. 2. Check the wiring for continuity.
- 3
Replace if needed, then reset
1. Replace a stuck or electrically failed IACV. 2. Clear the code and let the idle relearn.
Frequently asked questions
Why does my scooter stall at stoplights with code 29?
A dirty or failed IACV can’t add the idle air the engine needs when you close the throttle, so it stalls. Cleaning the valve often fixes it.
Last updated July 15, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.