Cummins SPN 1322 FMI 31: Meaning, Causes & Fix

Yes. A failing crankshaft position sensor can cause the ECM to incorrectly detect misfire events, even when all cylinders are firing properly. This is particularly common on engines with high-mileage CKP sensors that have degraded signal strength. Always verify with a cylinder cut-out test and compression check before replacing injectors or doing internal engine work.

A single cylinder misfire allows limited driving to reach a repair facility, but you should avoid heavy loads and high RPM. Unburned fuel from the misfiring cylinder enters the exhaust and can saturate the DPF, causing regen failures and potential DPF damage. Extended operation with a misfire also risks cylinder wash-down, where fuel dilutes the oil film and causes accelerated ring and liner wear.

A single new OEM fuel injector for a heavy-duty diesel engine costs $400–$900, plus 2–4 hours of labor. Remanufactured injectors cost $250–$500. When one injector fails on a high-mileage engine (500,000+ miles), consider replacing all injectors as a set — the remaining injectors are likely approaching end of life, and replacing them all at once saves repeated labor costs.

Consider an overhaul when: multiple cylinders show low compression, oil consumption exceeds 1 gallon per 5,000 miles, or the engine has 800,000+ miles with recurring mechanical faults. An in-chassis overhaul (rings, liners, bearings) costs $12,000–$20,000, while a full out-of-chassis rebuild costs $18,000–$35,000. Compare this to the $8,000–$15,000 in cumulative repairs you might face by continuing to patch individual issues.

Cummins ISX15 recommends overhead adjustment every 250,000 miles or at the first sign of valve train noise. Detroit DD15 specifies 150,000-mile intervals. Volvo D13 recommends 200,000 miles. Adjusting valve lash on schedule prevents misfire codes, improves fuel economy, and extends valve train component life. A valve adjustment costs $200–$500 and takes 2–3 hours.

This CHECK AT NEXT STOP code allows continued operation to a safe service location, typically within 50–100 miles. Reduce engine load (avoid steep grades, reduce cruising speed) and monitor related gauges closely. If secondary symptoms develop — smoke, unusual noise, temperature spike — pull over immediately.

If addressed promptly at the next stop, permanent damage is unlikely. However, prolonged operation (200+ miles) with this fault active can escalate the issue. For example, DEF system faults will eventually trigger a full derate and speed limitation to 5 mph. Some CHECK NEXT STOP conditions degrade into STOP ENGINE faults if the root cause worsens — do not postpone service indefinitely.

You can attempt the diagnostic steps listed above. Many CHECK NEXT STOP codes have straightforward causes — low fluid levels, clogged filters, or loose connectors — that an owner-operator can address. However, if the code returns after clearing, the underlying fault requires professional diagnosis with a scan tool capable of viewing live data and freeze-frame information.