Field notes
Diesel mechanic field notes.
DEF, DPF, emissions diagnostics, APU repair, fleet operations, EPA compliance, and the practical realities of mobile diesel service on the I-80 corridor.
What to do when your DEF light comes on
An amber DEF light isn't an emergency. A 5-MPH derate is. Here's what each stage of the DEF warning sequence means, how long you have, and what to do at each point.
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Cummins fault code SPN 3361 — what it means and how to fix it
SPN 3361 points to the DEF dosing valve. The fault has three common root causes — the valve itself, the wiring/connector, or a clogged dosing line. Here's the diagnostic flow.
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How to find a 24/7 mobile diesel mechanic on I-80 in Nebraska
Not every mobile mechanic listing on Google is actually 24/7. Here's how to verify before you call, what to expect on a roadside call, and what info to have ready.
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DPF regen failed — what now?
A failed parked regen isn't the end — but ignoring it is. Here's the progression from "regen needed" warning to forced derate, and what's fixable roadside.
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Cost of replacing a steer tire on a Class 8 truck (Nebraska 2026 pricing)
A blown steer tire on I-80 costs a lot more than the same tire in a shop. Here's what shop, mobile, and roadside service actually cost in 2026 — broken down by tier.
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Should you ever do a DEF delete? (Spoiler: no, here's why)
The DEF delete pitch sounds good: more power, no derates, no DEF cost. The reality includes federal fines up to $4,819 per truck per day. Here's the full math.
Read article →How long can you drive on a DEF derate?
Short answer: hours, not days — and it depends on which stage. Here's the practical timeline from first warning to 5-MPH crawl mode, by manufacturer.
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Thermo King APU not starting — common causes
Thermo King TriPac and TriPac Evolution failures fall into a predictable order. Here's the on-truck diagnostic flow that resolves 90% of no-start calls.
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NOx sensor replacement cost and DIY vs mobile service
NOx sensors are theoretically a DIY job. Practically, the scan-tool regeneration step is what trips most owner-operators. Here's the real DIY vs mobile cost comparison.
Read article →Eastern Nebraska truck repair guide — Lincoln, Omaha, Grand Island
Eastern Nebraska truck repair is concentrated in three metros — Lincoln, Omaha, Grand Island — with thin coverage between. Here's the practical map.
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What fleet maintenance directors actually look for in a mobile mechanic vendor
Vendor selection at a fleet of 50+ trucks isn't "who has the lowest hourly rate." Here are the six things maintenance directors actually score on, in order.
Read article →EPA compliance for mobile diesel mechanics — what fleets need to know
EPA enforcement on aftertreatment tampering doesn't just hit fleets and owner-operators — it hits the mechanics who do the work. Here's what compliance looks like in 2026.
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