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How to diagnose terminal connection problems in vehicles

Thursday, November 1, 2018 - 07:00
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When we think of failures, we often thing in terms of components since most of the time, that is what ends up being replaced especially with ignition problems and crank no-starts. Often times we overlook or never consider something that is becoming more common and that is the terminal contact inside of the connector to a component. The intermittent nature of terminal connection problems make them extremely hard to diagnose since they often occur so fast and also so randomly. One technique is use an oscilloscope to help pick out quick glitches in a circuit that would be hard to locate with other testing methods.

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2013 Dodge Durango

The first vehicle is a 2013 Dodge Durango with a 5.7L engine and 52K miles on the odometer. It was towed in with a complaint of a crank-no start. The customer stated the vehicle has been running rough and had low power before it stalled. When I went outside to try to start the Durango, it started right up like most technicians have experienced with a vehicle that was towed in and as most technicians would, I instinctively thought that a fuel pump was going out.  Something else that I noticed was I could not shift out of park, but after repeatedly pressing the brake pedal the shift interlock released so I could move the vehicle.

The 2013 Dodge Durango with a 5.7L engine

When I went to pull the Durango inside it died out while making a turn. I noticed a long crank before it restarted, then after about 20 feet it stalled again and this time it would not restart. After getting some help to push the vehicle in my bay, you guessed it; it started up and idled fine. Ok, let scan the vehicle for codes and take a look at some data before testing the fuel pump. I found a stored code P0627 Fuel Pump Relay Circuit which seemed in tune with the stall and long crank that followed afterwards. Also stored was a P0571 Brake Switch Performance code which explained why I have difficulty shifting out of park.

A good first step is retrieve Diagnostic Trouble Codes (DTCs) that give some direction in deciding where to begin testing.

Shortly after the vehicle was inside the service writer came with some information that the customer has shared with them. The customer informed us that the vehicle had been brought to the dealership earlier in week to have a fuel pump relay recall performed. They only had it back for a day when the stalling started occurring intermittently and then last time it stalled, it would not restart, only crank. We were also informed that prior to being at the dealership for the fuel pump relay recall repair, they did not experience any problems.

The fuel pump relay was originally an integral part of the TIPM, but when the safety recall has been performed, it is visibly mounted on the right front of the engine compartment.

On these vehicles, the fuel pump relay is integral to the Totally Integrated Power Module (TIPM) and is not serviceable separately. It appears that the fuel pump relay is problematic and a recall had been issued for this vehicle. Safety Recall R09/NHTSA 15V-115 addresses this problem, but instead of replacing the entire TIPM assembly, the repair is to rewire some of the TIPM circuits and add an external fuel pump relay.

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