Field Archive · 2023–2025

Case Studies

Selected investigations. Vehicles redacted where customer confidentiality applies.

Intermittent No-Start

Concern: Random no-crank events during cold-soak conditions. Two shops had already replaced the starter motor and battery. Symptom returned within 9 days.
Findings: CAN-low pull-up resistance degraded at the central gateway module. Start-authorization message intermittently dropped during the first 800ms of key-on, only at <5°C ambient.
Outcome: Central gateway replaced, network re-validated under thermal load chamber simulation. Zero recurrence in 90-day follow-up.

Concern: Multiple UDS no-communication faults across powertrain modules. Previous shop quoted a full engine harness at $11,400 + labor.
Findings: Single chafed termination-resistor wire in the B-pillar harness routing, isolated via PicoScope differential probe and time-domain reflectometry. Bus impedance restored after repair.
Outcome: Single-point splice repair. Quoted harness replacement avoided entirely. Repair cost: $340.

Concern: Recurring P0299 underboost code. Three turbochargers replaced under and out of warranty over 18 months. Symptom always returned within ~2,000 miles.
Findings: Boost reference vacuum line developed a micro-leak only under sustained load + heat soak. Confirmed via smoke test at temperature + pressure-decay holding under simulated load.
Outcome: Reference line replaced with PTFE-lined hose. Boost target sustained across 14 logged WOT pulls in follow-up validation drive.

Concern: Intermittent harsh 2-3 upshift, no fault codes logged. Dealer recommended valve body replacement at $6,200.
Findings: TCM adaptation values out of range due to a previous battery disconnect without proper relearn. Live trans-temp and line-pressure logging confirmed valve body was functioning correctly.
Outcome: Full adaptation reset and supervised relearn procedure performed. Shift quality restored. Total time: 2.5 hours.

Concern: Vehicle dead after 48 hours of inactivity. Two batteries replaced. Two shops unable to locate parasitic draw.
Findings: Front passenger door latch micro-switch occasionally failing closed, keeping infotainment module partially awake. Draw measured at 380 mA — 5x normal sleep current.
Outcome: Latch assembly replaced. Verified 72 mA sleep current after 4-hour shutdown sequence.

Concern: Fleet operator experiencing 6-week MTBF on DEF heater failures across multiple vans. OEM had no TSB.
Findings: Pattern correlated with vans operating on a single fuel supplier's biodiesel blend. Heater elements failing from contaminant deposition, not electrical fault.
Outcome: Fuel supplier changed for affected vans. Zero DEF heater failures in following 8 months. Estimated $42k annual savings.

If it's been quoted twice and still isn't fixed — start here.