APRIL 2024 AFTERMARKET 31 supply this can quickly identify we have an open or high resistance internally within the solenoid. As I had no fault code for the valve it showed the return wire to be intact to the control unit. This is how the ECU itself does a circuit check to set a fault code. It looks to see the supply voltage that is sent out return on the other wire to show circuit integrity. However, upon starting the engine the control unit did not attempt to control the solenoid by applying a PWM signal. Testing the solenoid itself by applying power and ground to it showed that it clicked and operated so it was in working order. Why then was the control unit not attempting to control the solenoid on start-up as expected? It was at this point I decided to step back and reevaluate things and go through what could possibly cause the issue. We could have an input issue stopping the ECU from commanding the solenoid, or an internal fault in the ECU. But what about the possibility of the connector for the turbo actuator solenoid being connected to the wrong component? Using wiring diagrams, I could check to see if the wiring colours match on my vehicle which would prove it. Carrying out a visual inspection, I noticed a solenoid close by which was identical to the one I had been testing, there was now a high chance we had a mis-match and the wrong connector was on the wrong solenoid. This would explain the lack of control and also why no other fault codes were stored as with both solenoids working and connected there was no reason for a fault code to be stored. After consulting wiring diagrams and wiring colours, I did indeed have an issue. The other solenoid was for the EGR bypass exchanger and the wiring colours matched the plug on the solenoid I had been testing. Disconnecting my connector on the turbo actuator solenoid and reading fault codes I confirmed it was indeed the EGR circuit. Please refer to Fig.2. I then disconnected the EGR solenoid and re-read codes which now logged an open circuit turbo actuator fault. Please refer to Fig.3. I then reconnected the wiring connectors onto the correct solenoids and retested the system. Now on engine start up the solenoid for the turbo control applied vacuum to the turbo itself which could be seen monitoring live data for the demanded and actual position of the turbocharger waste gate. Please refer to Fig.4 Road testing showed the vehicle could now create boost and have the get-up-and-go you would expect from a turbocharged engine. Returning to the workshop and rescanning for fault codes showed no fault codes present so the issue had been rectified. Why the plugs were swapped over is anyone’s guess. As the connectors were identical, they fit either way. I can only presume someone previously doing work mixed them up by accident. On this vehicle as I knew how the solenoid operated I did not choose to refer to technical information early on in the process. In hindsight this may have led me to the issue quicker. If I had seen what the wiring colours were for each wire on the solenoid, I would have spotted the issue. Even so, in total the job took less time than it took for me to write this article. Like I always say, following a solid process and thinking logically and methodically will always lead you to the cause of the fault. www.aftermarketonline.net Fig. 4 Fig. 2 Fig. 3
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