PX engines are Cummins B6.7 and L9 with PACCAR calibration — which means their fault codes mirror Cummins mid-range codes while dealers route you to DAVIE4. Both tools work; here's the code list either way.
How PACCAR PX-7/PX-9 fault codes work
PX engines report standard Cummins-style SPN/FMI. DAVIE4 shows PACCAR overlays; INSITE shows the native Cummins view. The codes below are the Cummins-native references since they're identical across both tools.
Most-searched PACCAR PX-7/PX-9 codes
These are the codes technicians look up most. Every row links to a full code page with symptoms, ranked causes and step-by-step diagnostics.
| Code | Meaning | Severity | Common fix |
|---|---|---|---|
| SPN 3216 FMI 4 | NOx sensor voltage low | High | Sensor/harness |
| SPN 5246 FMI 0 | SCR derate inducement | Critical | Root repair + reset |
| SPN 3364 FMI 2 | DEF quality erratic | High | DEF test |
| SPN 3251 FMI 0 | DPF pressure above normal | High — soot overload | Forced regen, then inspect |
| SPN 641 FMI 7 | VGT actuator not responding | High | Actuator calibration |
| SPN 3242 FMI 0 | DPF intake temp high | Medium | Temp sensor/doser |
Tools that read and clear PACCAR PX-7/PX-9 codes
PX engines work fully with INSITE — often the better choice for shops already Cummins-equipped. DAVIE4 adds chassis-side integration on KW/Pete. For forced regens, both tools work; procedure in the regen guide.
Frequently Asked Questions
Is the PX-9 just a Cummins L9?
Essentially yes — same base engine, PACCAR-specific calibration and badging. Cummins documentation and fault codes apply directly.
Which tool is better for PX work, DAVIE4 or INSITE?
INSITE for engine depth (it's the native platform), DAVIE4 if you also need Kenworth/Peterbilt chassis integration. Many shops use INSITE for PX and reserve DAVIE4 for MX engines.