Fixing a Mitsubishi L200 P0638 Throttle Fault & P1498 DPF Overloaded

For business enquiries email [email protected] www.orileysautos.com In this post I walk through how I diagnosed a failed throttle actuator and cleared an overloaded DPF on this L200, using live data, a bit of common sense, and a pressure-fed cleaner. I had just finished with a Nissan Navara when this L200 arrived, so I stayed in diagnostic mode and got straight onto it. The dash was showing: * Engine management light * DPF warning light * Small smoke symbol The truck ran, but it felt flat and restricted. Setting up the diagnostic tool For diagnostics I used the Launch X431 Euro from www.launchtech.co.uk 1. Searched for Mitsubishi L200 and selected the correct year. 2. Confirmed it as a manual transmission. 3. Left the SRS (airbag) faults alone for now, as they were not related. Reading the fault codes * Power supply low voltage (likely a weak battery at some point) * Throttle actuator control fault, marked as active * DPF overloading With an active throttle fault and a DPF overload, I knew these two were likely linked, so I ordered a throttle body early in the afternoon so it would be ready if needed. Checking DPF pressure and soot load Next I went into the data stream and pulled up: * DPF differential pressure * Soot loading values At idle, the DPF backpressure sat around 10 to 15 mbar. When I held the engine at about 3,000 rpm, it jumped to around 100 to 105 mbar. That is too high, so the DPF needed cleaning. Proving the throttle body fault I could not find any useful live data for the throttle actuator on this model, so I went old school. I removed the intake pipe to expose the throttle flap, started the engine, then turned it off while watching the anti-shudder valve. It should snap shut as the engine stops. It just sat there. No movement at all, only a faint buzzing. In other words, dead. Electrical checks on the actuator To be sure, I pulled the battery and casing out to access the connector and checked the wiring. * Main feed: 12 V present * Pin 2: 12 V * Reference: 5 V signal present Power and signal were fine, but the motor did nothing. That confirmed the throttle body itself had failed. Fitting the new throttle body Before fitting it, I turned the ignition on and watched the flap move as it ran its self-check, closing as it should to shut the engine down. Fitting it was simple: four bolts, one plug, and a small bracket. The old unit was a bit oily around the bore, which is common on these. Preparing for DPF cleaning With the throttle issue sorted, I moved back to the DPF. I located the DPF pressure sensor on its bracket and followed the pipe to where it enters the exhaust. That port is ideal for introducing cleaning fluid, as it feeds straight into the DPF area. There is usually a small pre-cat section, then the main DPF below. My “secret blend” DPF cleaning mix For the clean I used Launch UK DPF fluid. In the workshop we add our own little mix of “herbs and spices” to make it more effective. That recipe stays with me, but it does work very well. Injecting the DPF cleaner and watching the data I disconnected the electrical pressure sensor, connected a rubber hose to the pressure pipe, and attached my fluid gun set to about 120 psi. Back in the live data, the DPF differential pressure had already dropped to about 5 mbar at idle. That is exactly where I want it. After a bit more time at raised revs, the smoke cleared, which told me the DPF had dried out. Why this DPF blocked in the first place This DPF did not block for no reason. The throttle actuator failure put the L200 into limp mode and triggered the engine light. Once the management light is on and the engine cannot run a proper regeneration, soot builds up fast in the DPF, leading to an overload condition. Other DPF problems can come from: * High mileage and ash build-up * A damaged DPF core * Constant short trips that interrupt regens Reset, reinitialisation and final checks With good DPF pressure and a new throttle body installed, I went into special functions in the diagnostic menu. First I ran the throttle value initialization: I then used the DPF function to reinitialise the DPF values, so the ECU now thinks it has a clean filter. After that I cleared all the fault codes, cycled the ignition, and started the engine again. Road test and wrap-up To finish, I took the Mitsubishi L200 for a 4 to 5 mile test drive. Power was back, the truck pulled well through the gears, and no warning lights returned. Live data still showed low DPF pressure, which confirmed the clean had worked and the throttle fault was gone.