February 2022

FEBRUARY 2022 AFTERMARKET 35 Dodge this With this knowledge, I was already relieved that we didn't just replace the fuel pump. This car has only covered 18,000 miles from new despite it being a 2006 registration, so we already know the fuse is okay as the crash switch is closed. The next part of the diagnosis was to check the relay to see what was happening there. With the ignition cycled, no click was heard or felt at the fuel pump relay. As a result, I removed it and checked we had NBV at terminal 30. It was ok so I bridged terminal 30 and 87 with a fused link. With the amp clamp and a scope, I then joined up the bulb tester inside. The vehicle lit up and the pump worked; The engine fired up and the scope trace showed a nice even trace of the fuel pump commutator. There were no drops or missing segments (see Fig.2). Next, I checked the control side of the relay in the fuse box with another trusty bulb tester and a multimeter in parallel. Again, the car started, and there was no control circuit operative. So there is the fault, now to find the cause. First thing to do was check the wiring diagram again. With this we could see it was ground side switched from the ECU. Using the multimeter, it was found we had a permanent live on one terminal as soon as the ignition was turned on and we were missing a ground signal from the ECU. Everything that has a beginning... To gain access to the engine control unit, which just so happens to be on the opposite side to where my info showed it to be, I needed to remove the requisite trim. I was now faced with a tamper-proof bolt before removal of the ECU and connector. However, what struck me first was the amount of water around the area of the control unit. It is attached to the A pillar area just below the windscreen. (see Fig.3). A while later with the ECU in my hand and signs of water in the aperture of the connector pins, I load tested the wire from the ECU connector to the relay. I did this by applying a ground, and the test light in the control circuit lit up, confirming all was okay in the wiring. I proceeded to open up the ECU. Once opened, the damage could be seen to the board and components. Fault found, no parts needlessly fitted (see Fig.4). ...Has an end The outcome of this diagnosis was that the customer chose not to repair the vehicle as it was only used occasionally. With water intrusion issue also needing attention, it was just not worth the outlay to them. Despite this, I thought it was still worth sharing as a procedural explanation on the way I try to logic it out and approach a problem. A procedural explanation on the way I try to logic it out and approach a problem ” Fig 2. Fig 4. Fig 3.