P24E5
- Powertrain
- Manufacturer-specific
- Emissions
Diagnose soon
Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
NH3 Sensor Circuit Intermittent/Erratic
This code is in our catalogue but has not yet been through editorial review, so the guidance below is limited to what our structured data supports. We publish deeper diagnostic content only after a code has been reviewed — here is why.
The ammonia (NH3) slip sensor downstream of the SCR catalyst delivers an intermittent or erratic signal. The ECM expects a smooth voltage proportional to ammonia concentration in the tailpipe — sudden jumps, dropouts or noise mean the wiring, connector or sensing element is failing. Used to close-loop the AdBlue/DEF dosing strategy.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
- Urgency
- Diagnose soon
- Will it pass emissions
- No
- Check engine light
- Solid
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Corroded or loose sensor connector | Very common | — |
| 2 | Chafed or vibrating harness near the exhaust | Common | — |
| 3 | Aged ceramic sensor element drifting under heat cycles | Common | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
- Nh3 Sensor
- Sensor Wiring
- Sensor Connector
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Awaiting review
Found something wrong? Tell us — we publish corrections.