2004 Ford F250 5.4 Liter, Engine Stalls, Code P0231

This 2004 Ford F250 with a 5.4 liter gas engine came in with the complaint that the engine would occasionally stall. Testing found a code P0231 stored which indicates a problem with voltage to the fuel pump. Studying a wiring diagram showed several things. Number one is that when the fuel pump relay is engaged it supplies power to two different wires. Both dark green with a yellow stripe. One wire goes to the fuel pump via the inertia switch and the other goes to the PCM. If the code P0231 was stored and there was no performance problem with the fuel system the problem could be in the wiring between the fuse box and the PCM. In this case there was a complaint of an intermittent engine stalling condition so that meant the issue was related to the fuel pump relay. The second thing was that the fuel pump relay is built into the fuse box and is not readily serviceable. Time for an inspection.

There are four screws that hold the fuse ox to the underside of the dash. They all have 10 mm heads.

There is a battery wire at the far left end of the fuse box that has to be removed. I recommend disconnecting the battery before doing this. The plastic cap that covers the terminal and stud is a bit of a pain to remove and I used this hooked tool to release the latches. I released the one on the underside first and then the one I am working on in the following picture.

The 10 mm nut that holds the cable to the fuse box stud.

There are multiple harness connectors plugged into the backside of the fuse box assembly. There are several types of latches used to lock the connectors in place. All have latches that have to be depressed first except for one that has a loop on the end that has to be bulled up. It is the one to the far right in the next picture.

The fuse box out and sitting at my work station.

I like to mark the relays so that I can reinstall them in their original locations. I obviously also take a picture so that I know where all of the fuses go. The battery stud has to be removed before separating the plastic case halves. A couple of pocket screwdriver’s can be used to release the case latches and separate the two halves.

The fuel pump relay is the upper on to the right of the circuit board in the next picture.

There were 57 solder joints along the lower edge of the circuit board that had to be unsoldered in order to remove the circuit board from the rest of the fuse box. If you will enlarge the next picture and look closely at the leading corner of the right relay you should be able to see the melted plastic case.

From the backside of the board the heat discoloration can be seen along with a failed solder joint. Five more solder joints to desolder.

In total there were 62 solder joints that had to be unsoldered and then resoldered to complete this repair. I also reflowed and additional 57 solder joints on the mating board.

2013 Hyundai Tuscon, Blower Does Not Work

This 2013 Hyundai Tuscon came in with the complaint that the blower did not work.

A little bit of testing found that the blower did work on speed number one. Also the a/c led would light up when the switch was pushed on and the blower speed was set to one. The light would go out when the speed selection was increased. I did do some testing at the blower resistor however I did not take any pictures. No issues were found there.  Inspecting the blower switch meant removing a couple of panels to access the screws that hold the HVAC panel in place. I used a plastic pry bar to pull down the lower cover…..

….and the same tool to remove the Hazard switch panel above the HVAC control panel.

There were two screws at the top and two screws at the bottom of the control panel. Phillips head.

The HVAC panel then had to be popped loose from the dash with a little force.


I found this damaged connector at the rear of the blower switch portion of the HVAC panel. The switch also had heat damage.

The wires only had a little heat discoloration and it only went back an inch or two on a couple of wires.

I called the locale dealership and was told the connector was not available and the switch was only available as part of the whole panel. Since I had to look for a good used harness connector we also opted to find a good used control panel. It took a few days of searching to find a salvage yard that was willing to supply both.

I cut and spliced the replacement harness into the original by staggering the splice joints…..

…and sealing the terminals with dual wall heat shrink tubing.

I had to play around with the original and the replacement control panel to get the best looking exterior parts.

In the end it all worked well and looked good. I was happy and more importantly the customer was.

2005 Ford F150-Turn Signals Inop with Headlights or A/C On

This 2005 Ford F150 came in with the complaint that the turn signals would stop working whenever the headlights were turned on. The customer also stated that the a/c did not work. Inspection found that the turn signal indicators in the instrument cluster would would come on at about half brightness when ever the lights are turned on and if the a/c controls are used. Also the high beam indicator would illuminate similarly and the gauges would move as the switches were turned on and off. The turn signals worked normally with all other switches turned off.

Following the wiring diagrams this ground point was located behind the right kick panel. That is a lot of rust for the inside of a vehicle.


It was so rusted that the metal let go as the attaching bolt was loosened.

We had to use pliers to hold the rusted nut and an impact on the bolt head to break this loose.

The bolt head wrung off during the process and left the terminals in tact. It did take a few minutes to separate and clean the individual ring terminals.

Since there was no place to secure the terminals near the original location I pulled the end cover off of the dash panel and secured the wires as shown below. I did have to ream the hole out slightly in the ring terminal in order for the bolt to fit. We followed up with inspection and cleaning of a second ground point located behind the driver’s kick panel. The metal was in pretty good shape over there. After the ground was repaired all systems went back to working correctly.

Some of the rust on the outside of the truck.

I know that this amount of rust is very common in other parts of the country but it is almost unheard of here in South Carolina.

2010 Ford Explorer-No Crank Condition- Fuse #8 and Otis Diode Blown

This 2010 Ford Explorer with a 4.o liter engine was towed in with the complaint that the engine would not crank. The vehicle owner had found that the fuse #8 in the interior fuse box was blown and the Otis or starting diode in the underhood fuse box had melted.

It took some effort to remove the melted diode using a pair of pliers to grasp it and and screwdriver to chip away at the melted seam. In the end it came out cleanly. I inspected the wiring underneath the fuse box and there were no signs of any heat damage.

The melted diode.

The diode should look like the part on the left in the following image. By the way the reason why the diode melted was due to the fact that when there is a short in the wiring the diode fail in a way that allowed it to flow current in either direction. Repeatedly replacing the blown fuse (with the correct or possibly a higher amp fuse) and trying to start the engine overheated the plastic until it melted.

I had used the good diode to the left for my initial test and it immediately blew when I tried the start the engine. The fuse also blew. Since the Ford diode cost about $5 I switched to using a cheap one amp axial diode for further testing. The stripe on the axial diode orients to the same end as the bar on the diode image on top of the factory diode.

I looked over the wiring diagrams and decided to go towards the transmission range sensor in order to start isolating some of the wiring. Also anywhere around transmissions and exhaust systems is always a likely place to find a short.

I disconnected the sensor and rechecked for a short by installing a new diode and fuse. They both blew when I tried to start the engine.

As a result of that test I moved towards the PCM to isolate the wiring at that location.  That is where I noticed a small harness and a metal bracket that just did not look right.

The angle in which the harness was laying in the metal bracket allows contact at a sharp edge of the bracket.

I first inspected the area closer using a mirror and flashlight before disturbing anything. It was pretty evident that there was a problem there. Sorry could not hold the flashlight, mirror and camera all at the same time.

Enlarging the following image should allow you to clearly see the white wire with a violet stripe that has been riding on the metal bracket until it cut through the insulation.

There is a harness connector that I disconnected in order to have easier access to repairing the damage. In the end the wire was not damaged enough to do anything more than sealing it with quality electrical tape. I sealed the single wire then wrapped the entire harness.

Covered the harness with split loom….


…and ultimately decided to reroute the harness away from the bracket.

A new diode and fuse and this one was fixed.

2008 Chevrolet HHR-Reduced Power-Code P0641

This 2008 Chevrolet HHR came in with the complaint that the check engine light would come on, the reduced power message would display and the car would no longer accelerate. There was a code P0641 stored.

The code p0641 means that the 5 volt reference is outside of the 4.8 to 5.2 voltage range needed to keep the PCM happy.  In this case I observed a 5.5 volt reading in the 5 volt reference 1 data line under PCM-TAC live data.

A little bit of searching and I found this connector located under the passenger side rear of the truck. Just in front of the rear axle area. It is the pass through connector for the fuel pump assembly.

The customer was not able to afford a proper repair so I took an air hose and blew the water and corrosion out of all parts of the connectors. To my surprise they actually came quite clean. I lightly scrapped the terminals down and installed some electrical grease in the  connectors.

This took care of the problem but I explained to the customer that the problem will likely return one day and more work will be needed to repair it correctly.

2006 Chevrolet Silverado-Driver’s Temperature Door Erratic

This 2006 Chevrolet Silverado came in with the complaint that the driver’s temperature door would shift between heat and a/c without the controls being adjusted. The actuator had been replaced with a quality ACDelco part. Testing found that the actuator counts on the scan tool would fluctuate when the actuator harness was wiggled around slightly.

There are two options for repairing this problem. First the connector can be replaced. The next option is to carefully disassemble the connector and tighten the terminals. First the red locking comb has to be removed.  a small screwdriver can be used to release the clip.

There is a special square tipped terminal tool for releasing the locking tab on the terminal. The end of a large paper clip could also work.

Once the locking tab is compressed and released the wire and terminal can be pulled from the connector body.

One of the first things I try to do once the terminal has been removed is to reposition the locking tab as shown below.

In the next picture I point to the location where the metal need to be pushed in towards the center of the terminal. This needs to be done on all four sides.

These are of course brand new terminals. If you are like me and do this for a living having these around to perform drag tests saves a lot of time.

The re formed terminal ready to go back into the harness connector.

I want to point out that when this condition occurs it is almost always caused by human interference. Some one brutishly handling the connector while replacing a part or a cover being missing and the connector repeatedly being moved.

2002 Ford F150-Dome Light Glows

This 2002 Ford F150 Super crew pickup came in with the compliant that the dome light would glow and the rear reading lights were always about half bright. If they were manually turned on they worked normally. The glowing/half bright condition was present with the ignition on or for about an hour after the ignition was turned off.

I performed all sorts of testing at the fuse box, the GEM located at the rear of the fuse box and at every interior light in the truck.

This is what I discovered after hours of searching. The next two images are of the side reading light harness connectors.

Notice the orientation of the green wires in the connector bodies.

The two reading light assemblies.

The rear of the two light assemblies.

Enlarging the images will allow you to see that the light assemblies are labeled as left (LH) and right (RH). Unfortunately even though they are labeled they can be installed at either location and in this case they were.

In the end the customer acknowledged that he had removed the headliner to have it recovered and must have put the lights back in in the wrong locations.  He had done this nearly a year ago so it did not have that brand new look or smell for me to pick up on.

2013 Dodge Charger-A/C Compressor Not Working

This 2013 Dodge Charger came in from a body shop to have the a/c serviced after the front clip was replaced. That service went fine and there were no problems until the car was being picked up. All of the data looked fine but the compressor was not coming on even though the data showed that it was.

I checked the a/c compressor fuse with the engine running and the a/c system on. As my test light touched the fuse I could hear the compressor engage.

This indicated a poor connection at the fuse itself so I removed the fuse for inspection. If you enlarge the following image you can clearly see the arc mark on the fuse that I am pointing to with my test light.

I scraped the matching arc marks off of the female terminals in the fuse box and used a pick to bend the tabs back in. Care needs to be taken to make sure everything stays square. I also installed a new fuse. The best way to fix this is to install a new fuse box assembly but the customer did not want to go that deep into this repair.

While I was in the fuse box I thought I might as well identify the a/c compressor relay location.

2009 GMC Yukon-Power Lift Gate Not Working

This 2009 GMC Yukon came in with the complaint that the power liftgate did not work and that the rear outside switch has already been replaced. It is the most common failure point in the system but not this time. Starting from scratch I checked the fuses and found that fuse #71 was blow. It is labeled as LGM (Lift Gate Module).

A common spot for random shorts on this series of trucks and suvs is located under the  driver’s side of the dash. Just above where the driver’s left foot would rest.

The wiring harness shown that I am pointing out gets pushed down against the sharp edge of a metal bracket  until it rubs through and shorts out.  I installed a good fuse and checked for power on the red/black wire to confirm I had found the correct short.

Enlarging the following image shows the damaged spot on the red/black wire insulating jacket.

A little bit of electrical tape and some split loom was all it took to fix this short.

1995 Chevrolet Caprice-Engine Stalls

This 1995 Chevrolet Caprice came in with the complaint that the engine would stall if the headlights were turned on or if the brake pedal was depressed.  The problem was also intermittent. The strange  thing was that it would feel like the engine was  running out of fuel rather than just an instant turn off.  I did a little research into the problem and found a reference to a shared ground at the left side of the trunk.

After locating and inspecting the shared ground I found that it was loose and was definitely the cause of the problem. I cleaned and tightened the connections and the issue was resolved.

To clarify the grounds at this location were for the rear lights and the fuel pump. Also not seen in the above image is the large speaker enclosure that would  move around in the trunk and had bumped into the wiring causing the screw to loosen.