Intermittent Underboost and a Customer Who Wants the Code Cleared
A 2018 2.0 diesel delivery van has intermittent limp-home with the glow-plug light and an engine fault message, often on the same hill at about 2,500 rpm under load. Two months ago another garage replaced the turbocharger after finding a P0299 underboost code; the fault returned after 600 km. Current codes are P0299 stored and P0238 (boost sensor circuit high) pending. Freeze-frame shows 2,410 rpm, 88% accelerator, actual boost 1.15 bar, desired 1.75 bar, intake air 58°C and fuel rail 1,150 bar. The customer is a courier who loses about £180 a day when the van is off the road, has already paid £1,400, and demands that you "clear the code and let me run it" while he waits. During the check you also find front brake pads at 1.5 mm and a front tyre at 1.6 mm with cord visible on the inner edge.
1. Analyse the freeze-frame and set out the next diagnostic steps. Why is clearing the code not an acceptable repair?
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The freeze-frame shows a genuine load condition: 2,410 rpm and 88% accelerator, with actual boost 0.6 bar below desired. That supports an underboost fault rather than a low-load glitch. The pending P0238 is equally important: a boost sensor circuit high can be caused by a faulty sensor, a short to voltage, a poor ground or reference fault, and it can distort the boost reading the ECU uses for control. First check sensor rationality with key on, engine off: manifold pressure should be close to barometric. Then inspect the intake for restriction, check boost hoses, intercooler and clamps for leaks, and check the VNT actuator and vacuum supply. Test exhaust backpressure and check for a restricted DPF. Use live data under load and a smoke or pressure test. The previous turbo replacement makes installation and control faults more likely than a second failed turbo. Do not clear the codes while diagnosing: that erases the freeze-frame, readiness status and pending evidence, and it does not repair anything. Clearing may get the customer moving briefly, but the fault will return, possibly during a delivery, and the next garage will have less information.
2. How would you handle the customer's demand and the two additional safety defects?
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Acknowledge the lost income and the £1,400 already spent, then separate the issues clearly. Explain that clearing the code is not a diagnosis and that the freeze-frame is valuable evidence; offer a fixed-price diagnostic with live data and a boost leak test, and give a realistic time. If a loan van is available, offer it. For the brakes and tyre, do not soften the message: 1.5 mm pads and a tyre with cord visible are safety-critical and likely illegal to use on the road. Show the customer the parts, record the measurements, and provide written advice. Offer same-day replacement if parts are available. If the customer refuses, document the refusal and the warning that the vehicle should not be driven, and consider arranging transport rather than allowing a road test. Check whether the previous turbo repair carries a warranty and whether the original fault was properly diagnosed. Keep the tone professional: the customer is under pressure, but releasing an unsafe vehicle or clearing codes to end the conversation would expose him and your workshop to serious risk.