Toyota Avensis Verso D4D: Danger to life in emergency mode

Toyota Avensis Verso D4D: Danger to life in emergency mode

At the Carinthian Packsattel, every driver's nightmare became reality: in the middle of the motorway tunnel, on a road with no hard shoulder, the engine control light in the cockpit of a Toyota Avensis Verso D4D suddenly lit up and the speedometer needle quickly fell from 100 to 15 km/h. Luckily, the story ended well because the truck behind the compact van was able to brake in time. Nevertheless, the shock of the Toyota driver remained in his bones for a long time. When he drove out of the tunnel at a snail's pace in emergency mode and was finally able to park the car on a hard shoulder, he tried to restart. To his surprise, the engine worked smoothly again and the check engine light no longer came on. It's no wonder that the driver still went to a specialist workshop because he didn't want to experience such a situation again. Our diagnostic crime thriller began there, which this time has two chapters.

Chapter 1

1. When the vehicle was connected to a diagnostic tool in the workshop, it only showed a fault with the fuel pump (code P1229). 
2. The workshop then consulted the AVL DiTEST vehicle hotline, whose experts had already gained relevant experience with the symptoms described. The suggestion that the cause could be defective suction lift control valves (SHSV) turned out to be spot on.
3. After replacing the SHSV, the problem no longer occurred for the time being.

Chapter 2

1. After a little more than a year, problems with the engine control occurred again: especially in cold temperatures, the car went into emergency mode after a few seconds of idling and coasting, which caused the driver to hear many a honk in city traffic. 
2. First suspicion: Since the new problem always occurred when the accelerator pedal position was at 0, a malfunction of the accelerator pedal sensor could be to blame. 
3. Reading the fault memory revealed the following entries: P1229 fuel pump and P1250 turbocharger system.
4. A quick check of the accelerator pedal position using error reading and a re-measurement using an oscilloscope showed correct results. The diagnostic values ​​of 17% idle and 75% full load are OK for this type according to the AVL DiTEST information system.
5. The rail pressure at idle was checked with an oscilloscope. Conclusion: When starting, the rail pressure rose very steeply and quickly and remained more than a third above the target value when idling.
6. Since the ECU intervenes in the rail pressure control via the SHSV, the control of the SHSV was now compared with the reference curve in the oscilloscope. Conclusion: The SHSV were not activated when idling because the rail pressure was already too high. Activation only occurred during the starting process and at increased speed.
7. The cause was now clear: The SHSV suction lift control valves should be closed when de-energized. However, since the rail pressure did not decrease when the SHSV was not activated, the control unit set an error and the vehicle went into emergency mode.
8. The case was finally resolved with another exchange between the SHSV.

AVL DiTEST expert tip

Practice has shown that the suction stroke control valves can fail due to mechanical defects or contamination despite perfect electrical function. Defective valves can lead to starting problems, rough running of the engine or a lack of power. In addition, an unusual rail pressure curve can often be seen, such as fluctuating rail pressure when driving at constant speed. In these cases, the valves must be replaced despite faultless electrical function.