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.
Charter Bus AC Died in July Heat Near Lincoln — Back Cold in 4 Hours
A charter coach lost its AC completely in July heat and had to drop the whole group at a hotel. We came to the bus, diagnosed and repaired the system on-site, and had cold air flowing again in about four hours — same day, trip saved.
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Trailer Door Won't Seal in Lincoln? We Fixed It and Renewed His DOT Inspection Same Sunday
A Sunday call from an out-of-state driver caught two out-of-service problems at once: a trailer door that wouldn't seal and an annual DOT inspection expiring in three days. Here's how we handled both on the spot in Lincoln.
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DEF Full but Still in a 5 MPH Derate? SCR Conversion Fault on a DD15 at I-80 Exit 401
A 2020 Cascadia DD15 dropped into a 5 MPH derate at the TA on I-80 Exit 401 with a full DEF tank. The problem wasn't fluid — it was a clogged doser and a lazy inlet NOx sensor. Here's how we got the driver rolling the same evening.
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DEF Light Stayed On After a Refill? Why a Bad Jug Dropped This Kenworth to 5 MPH on I-80
A driver topped off DEF at the truck stop but the amber light stayed on and the Cummins X15 dropped to 5 MPH climbing the I-80 grade west of Grand Island. It wasn't a level problem — it was a DEF quality fault a refill can't clear.
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On-Site Fleet Tire Replacement in Lincoln: Drives Swapped Without Losing a Dispatch Day
A Lincoln distribution fleet needed worn drive tires replaced across several day cabs without pulling trucks off the board. We brought the tire service to their yard and had the whole group back to legal tread in one half-day visit.
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When a Forced Regen Won't Complete: Cleaning a Face-Plugged DPF on a PACCAR MX-13
A 2019 Kenworth T880 kept throwing regens until a parked regen flat-out refused to finish. The fix wasn't another regen — the DPF was face-plugged with ash and had to come out and get cleaned.
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Steer Tire Blowout on I-80 Through Lincoln: Mobile Replacement in Under an Hour
A loaded 2022 International LT lost its right steer tire to a road-hazard cut on I-80 near Exit 397 in Lincoln. We dismounted, mounted, balanced, and torqued a new steer on the shoulder — back rolling in under an hour with no tow.
Read article →Catching a Volvo D13 Outlet NOx Sensor Failure Before It Derated (SPN 3216)
A 2021 Volvo VNL threw a stored SCR/NOx fault at a Lincoln PM with no derate yet. We replaced the failing outlet NOx sensor, stopped the inducement countdown, and kept the truck out of a roadside limp-mode situation.
Read article →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.
Read article →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.
Read article →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.
Read article →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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