1989 Ford Ranger XLT, 2.9, Brake Lights Inoperative

We had this 1989 Ford Ranger XLT with a 2.9 engine come into the shop with a customer concern of no brake lights.

I decided to start my diagnostic at the stoplight switch. I could have started at the fuse, but if I have voltage at the switch my fuse is good. (I already knew the bulbs were good, we had replaced one, so I wasn't worried about them.)

When I checked the stoplight switch without the brake pedal depressed, I found voltage on one wire and ground on the other. This is normal and what we would expect to see. Below, you can see me testing the two circuits with a PowerProbe.

First, the circuit with voltage. (Notice the red light illuminated in the top right of the Probe and the reading on the face at 12.6 v.)

Next, the ground circuit. (Notice the green light on the top left of the Probe illuminated, along with the reading of 0.0 v.)

So far, so good. This is as it should be. Again, this shows my fuse to be good (because we have voltage) and we have a good ground circuit as well). So, at this point, I am not concerned about my fuse or the wiring from the fuse to the switch, all that is good.

The next step in the diagnostic is to load the circuit by depressing the brake pedal. When this is done the switch should activate and allow voltage to flow. So then, when testing it with the Probe, we should see voltage on both circuits.

However, when we depressed the pedal (applied the brakes) the circuits remained the same as above: that is, one circuit showed voltage and the other still showed ground.

Below you can see that the brake light is not illuminated.

When I unplugged the switch and applied voltage to the ground circuit, the brake lights illuminated.

This proved that the stoplight switch was faulty and needed replacing.

After I replaced the switch, I once again depressed the pedal, unlike before, now both circuits showed voltage.

Below is the first circuit, clearly showing voltage.

Next, is the second circuit, which before had remained ground, but now shows voltage (as it should when the switch is working properly). (Sorry it is a bit blurry.)

Now, with the switch working properly, the brake lights were illuminated.

We put everything back together and another job was done!

2005 Ford F150 5.4, No Crank/No Start

***This post will be a short write-up as FYI. It will not be as detailed as most posts.***

This vehicle, 05' Ford F150 5.4, came into the shop with a customer concern of a no crank/no start condition. Let me first give you the details of the complaint history.

The customer stated he had driven the truck as he normally does and parked it in the garage. The truck sat in the garage for a day or two. When he went out the next time to drive it, the truck would not crank over. When he would turn the key to the start position nothing would happen. He checked the battery and it was good.

He and a friend checked out a few fuses and a few other things but could not find the problem.

He called me and had the vehicle hauled to the shop.

When the truck arrived at my shop the battery was down (from the customer trying to start it numerous times); so, first things first, I replaced the battery. It was time to perform some diagnostic tests on this vehicle.

Next, I had an assistant turn the key to the start position and probed the wires at the starter solenoid. I found there was no voltage to the starter solenoid, it had ground all the time.

I then pulled a wiring diagram and checked the pertinent fuses for the starting circuit. All tested good. Next, I used a relay tester and checked the circuitry at the starter relay. I noticed the contacts that normally should show a ground when the key is not in the start position, were showing nothing at all.

The fuses and relays are located behind the kick panel on the right (passenger) side. See the picture below:

Next, I checked the fuses for the PCM and all were good. I had tried communicating with it with my scan tool, but had received an error message for "No Communication".

I then tested the PCM relay and found the problem. The PCM relay was not working. It had power to the relay, but the relay was not internally switching. I bench tested the relay and the first couple of times it tested faulty. I tapped it lightly a few times and it came to life.

In the pictures below is the relay:

I replaced the relay with a new one.

In the pictures below you will see where the relay is located in panel. (It is number 203 on the cover legend.)

Viola, the truck then cranked over and started right up!

2000 Chevrolet C3500 5.7, Wipers and AC Inoperative

This 2000 Chevrolet 3500 came into the shop with a couple of complaints by the customer. He said that a few days before both his AC and windshield wipers stopped operating.  He had checked a couple of fuses, but was unable to find a problem.

First things first, I confirmed the customer's concern.  The AC and the wipers were inoperable.  Next thing to do was to pull up a wiring diagram and start checking the circuit.

I first checked out the two fuses in the fuse block on the left-hand side of the dash.  The wiper and AC fuse are next to one another.  At first, I wondered if something might be going on with the terminals.  When I checked the fuses (Fuse 11 Wiper 25A and Fuse 12 HTR-AC 25A) with KOEO (Key On Engine Off) and the AC and wipers in the on position, I got ground.  No power was coming to the fuses.

Now that I knew there was no power to these two fuses, it was time to find out what their power source was.  Again, consulting the wiring diagram, I saw power was supplied to these circuits by the IGN B 50A fuse.  I saw the radio was also powered on this circuit, and when I checked the radio, as expected, it did not work either.  The IGN B 50A fuse is located in the Power Distribution Box under the hood, on the left (driver's) side of the engine compartment.

The fuse I'm pointing out is the IGN B fuse.  When I checked it with the Power Probe it showed one side with power and the other side without.  This meant we had a blown (melted) fuse.  I replaced the fuse, turned the key to KOEO and tried the problem circuits.  They all now worked.

Of course, fuses don't just blow for the fun of it.  When I reported my findings to the customer, telling him we would need to do further diagnostics to determine the cause of the blown fuse, he opted to pick it up and run it until he has any more trouble out of it.

I advised him on the potential problems and inconveniences that could result from this; but, he decided to pick the truck up as is anyway.

I just hope it doesn't decide to blow when it's raining!

2002 Chevrolet Cavalier 2.2, Engine Light on with a P0440 Code Stored

This 2002 Chevrolet Cavalier 2.2 came into the shop with a DTC P0440 Evap Emissions System Fault.  The first thing we did was to give a visual inspection of the EVAP system.

We did not see any obvious problems, such as, broken or disconnected hoses, unplugged components (i.e. purge or vent solenoid), broken wires, or loose/missing gas cap.

Many people, when presented with this code, will automatically replace the gas cap.  While these caps do need replacing from time to time for maintenance issues, this may not solve the problem.  In this case, the gas cap was not the issue.

We then decided to use our diagnostic tool and, using its bi-directional command capability, commanded the purge and vent solenoids on and off.  When we did, we heard (and could feel) each one turning on and off as we commanded it.  We did this several times to ensure there was not an intermittent problem with sticking in the solenoid.

Next, we connected our smoke machine, which we use to check for EVAP leaks.  Again, using the diagnostic tool, we commanded the vent solenoid on (which closes the valve . . . this valve is normally off and thus open, to do the test it must be "On", meaning the vent is closed, so as to allow the system to hold the smoke in), and tested the system with smoke.

The picture below shows the evidence.  It is a bit hard to see, so we have drawn an arrow to point to the evidence.  What we saw was smoke boiling out of the vent solenoid, even though we were commanding it "On", thus closing the vent.  Therefore, with the vent "On" no smoke should have been escaping.

With this evidence, we removed the vent solenoid.  What we found is that someone had tie-strapped the diaphragm.  More than likely, a previous owner (our customer said they had not done this) knew about the problem and tried to rig it to work.  Not a good idea.  The solenoid was actually leaking from around its diaphragm, so a new one was in order.  A picture of the old one, tie-strap still on is below.

The next picture shows the new vent solenoid in place.

  
Just FYI, there is a short wiring harness (see below) connected to the vent solenoid.  These are notorious for fraying and breaking, due to rear end movement.  Like the gas cap above, this was not the cause of this failure.  Silver bullet fixes usually end up costing a customer far more money than simply taking it in to a professional to have it properly diagnosed and repaired.

Here is the short wiring harness (I am pointing to it in the picture).

After completing the repair, we cleared the codes and data associated with it.  We then ran a EVAP system test with our smoke machine.  The test passed.  A picture of that is below.  You will notice the green lit LED indicating the test completed and passed.

There are many variables when it comes to diagnosing and repairing an EVAP system.  A basic understanding of how the EVAP system works on that particular make and model is essential.  A visual inspection is always the first place to start.

Don't jump at silver bullet fixes.  You may get lucky and it may be your problem and repair your vehicle.  Then again, you may spend quite a bit of money chasing several silver bullets and in the end be left with the original problem.

When in doubt, find a professional you can trust and take it to him/her and let them do the proper diagnostics and repairs.  It may end up saving you far more money in the long run.

I know the economy has been rough and times are tough.  But, throwing parts at a problem can compound that problem quickly.