P1477
Too Much Secondary Air.
- Jeep
- Powertrain
- Manufacturer code
- Low severity
How this code is built
- P
- SystemPowertrain
- 1
- Defined byThe manufacturer
- 4
- AreaAuxiliary emission controls
- 77
- FaultThe specific fault in that area
What it means
P1477 on a Jeep means the powertrain control module judged that more secondary air was being delivered to the exhaust than expected. It sets when the oxygen sensor readings during the secondary air test show a leaner exhaust than the system should produce. The system layout and test method vary by model, engine and market, so confirm the details for the specific vehicle.
Symptoms
- Malfunction indicator lamp on
- Possible whining or droning from the air pump area, or the pump running at the wrong time
- Slightly rough idle or poor running just after a cold start
- Failed emissions test or readiness monitors that will not complete
- Often no noticeable driveability change
Possible causes
- Secondary air injection check valve or diverter valve leaking or stuck open, letting air in when it should be shutlikely
- Air switching or control solenoid, or vacuum control, stuck open or failing to closelikely
- Faulty oxygen sensor giving false lean readings, or an exhaust leak upstream of the sensor drawing in airpossible
- Air pump running when not commanded, or a pump relay stuck onpossible
- Damaged or disconnected vacuum lines or air hoses to the secondary air componentspossible
- Wiring or connector fault in the solenoid, relay or sensor circuitsrare
- Fault in the powertrain control module or an outdated calibration where the manufacturer has issued an update for this coderare
How to diagnose
- Read all stored and pending codes and freeze frame data, noting engine temperature and load when the code set, and check for any oxygen sensor or fuel trim codes
- Check for technical service bulletins and calibration updates for the specific model and engine
- Visually inspect the secondary air hoses, vacuum lines, connectors and wiring for splits, disconnections, heat damage and corrosion
- Inspect the exhaust for leaks upstream of the oxygen sensors, especially at the manifold and flange joints
- Using a scan tool, command the air pump and solenoid on and off and confirm each responds only when commanded
- Check the pump relay and fuse, and test the power, earth and control circuits to the pump and solenoid
- Test the check valve and solenoid for leakage and correct vacuum operation, following the procedure for that engine
- Review live oxygen sensor and fuel trim data with the system on and off to check sensor response before replacing parts
How to fix
- Replace a leaking or stuck check valve or diverter valve
- Replace a faulty air switching solenoid or repair its vacuum supply
- Repair or replace damaged hoses and vacuum lines
- Repair any exhaust leak ahead of the oxygen sensors
- Replace a faulty oxygen sensor only if testing proves it is reading incorrectly
- Repair wiring, connectors or a stuck relay, or apply an official calibration update where one is known to cover this fault
Can I keep driving?
Low severity
The car can normally be driven while you arrange a repair, as this fault mainly affects emissions. Have it checked soon, especially if it is running roughly or you need to pass an emissions test.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.