The Long and the Short of It

The '02 Ford F150 comes in with no brake lights and no turn signals. First rule is usually, verify the complaint. There were no working brake lights. Even the third brake light at the rear of the cab was not working. Turn the key on and neither left or right turn signals were working. There also was no turn indicator on the instrument panel. No third brake lamp and no turn indicators made me think checking fuses would be a good idea. When I say *check*, I mean *test*.
There are a lot of different pieces in a fuse block.

Relays, diodes, cartridge fuses, blade fuses and a circuit breaker are all part of the underhood fuse block on this Ford. 

Now, I said the symptoms so far make it worth looking at fuses. I'm not going to worry about relays, diodes or circuit breakers at this stage of the game. I wanted just fuses. Cartridge fuses are designed so that you can look through a clear plastic window on top and usually tell if the fuse is okay or not okay. This one is okay. 

The look-and-see approach works most of the time. If things get questionable the top cover is removable for better surveillance. Just be careful not to break the plastic. The cartridge fuses looked okay in this underhood block so I wanted to test the blade fuses. You can also view inside a blade type fuse but you have to remove the fuse from the block in order to see if it is good or bad. 

If you start pulling blade fuses just to look... well, there are a lot of blade fuses and even if you pull one at a time it can easily be placed back into the wrong slot. I had a Jeep Grand Cherokee in just a couple days ago the problem turned out to be caused by an ABS fuse placed into the wrong space and the ABS fuse slot empty. There is also the problem of just looking for a fuse marked *Turn Signal* (in this case) and only looking at that one. Many fuses aren't that easily identified and if you do find a fuse marked for the system it could be a good fuse and the one causing the problem is a completely different fuse. You need to check all the fuses when you are testing and since the only part of the fuse readily accessible with the blade fuse in place is the shiny blade tip then you use a circuit tester and probe that tip. Do that and you won't misplace a fuse, you won't pull a lot of fuses and you will know if there are any blown fuses on other circuits causing a problem. 

First, grab a circuit tester suitable for probing the blade tips. I have a lot of circuit testers. 

 I even have a couple I made when I was a kid. Humor me. 

My favorite tool for this particular purpose though is my old Power Probe II. The leads connect directly to the battery, plenty of cable to go anywhere on the truck, a good ground lead at the probe end, switchable power or ground available to the probe tip and audible for when the circuit indicator isn't visible. I know, sounds like overkill but depending on where the diagnostics take us it could be a real time saver. 

Back to the problem at hand. I started with underhood fuses. I wanted to power to as many fuses as feasible prior to testing. Most fuses are either battery powered (hot all the time) or ignition powered (powered with key on). There are nuances, like battery power that times out. Or ignition power with key on accessory instead of *on* position. Or even ignition only in crank (start) position. In this case though I would have either battery power (brake lights) or key on ignition (turn signals) most likely bad. Turning the key on and testing blade fuses with the probe was all I needed to get started. Just touch the probe tip to each of the two blade tips of each fuse. If one side is hot (power), the other side should be as well. If one side is hot and not the other, bad fuse. The LED on the probe turns red for power, green ground. 

All the underhood blade fuses tested good. All the underhood cartridge fuses looked good. Time to move inside under the instrument panel. 

Found! Bad fuse. 

Technically in Fordspeak, that is the second fuse block (F2) and the #13 fuse. So fuse F2.13

Remember that for a test later. Just joking. If you were going to pull a wiring diagram you could pull up the circuit diagram for F2.13 and look for likely areas for shorts. 

Even though the brake lights and the turn signals worked after replacing the fuse I still was looking for why the fuse was blown in the first place. Fuses are there to protect the circuit. If the fuse blows there was some sort of overload because those fuses don't wear themselves out. This ain't my first rodeo though and it is a truck. The area where a short most likely to take out brake and turn lights would be is the rear. Especially if there is a trailer hitch and a trailer plug back there. 

I put a bar in place to hold the brake on. I slid under the rear of the truck with brake lights on and the plan became one of carefully examining the wire harness at the back of the truck while wiggling and pulling to try and induce a short if it did exist in that area. 

I found nothing with the brake lights on. I turned only the right turn signal on and tried again but only in the area under the right turn. Nothing. Okay, may as well try the left turn before I move on to something else. BINGO!

Fuse replaced. Short repaired. Longer arms and I could pat myself on the back. 

I can walk you through a wiring diagram. It wasn't needed here but it would still be interesting. 

Thanks!

Kenny@ggauto.repair

G&G Auto Repair

MIL or Check Engine Testing pt.2

So what is freeze frame data?

Sometimes when a trouble code is stored in the engine module on an OBDII vehicle there will also be a "snapshot" of the sensor readings at the time the code set in the system. Codes get different priorities and some more recent freeze frames may replace older ones. There is also that the system is basic (global) OBDII and the sensor data is pretty limited. With that disclaimer mentioned, you can still sometimes get a clue to what may be causing a problem. So it is worth a look if your tool supports it. 

We began with a basic OBDII code reader and the next step up will be OBDII code reader with freeze frame. For an example, here is a 2006 Toyota Matrix with a system lean code P0171. A P0171 is a trouble code that will set if a fuel mixture is too lean as indicated by the O2 sensor. Not enough fuel or too much air can set the code, if the system is working properly. 

If the condition appeared at idle or low rpm you can expect it to be too much air. A vacuum leak. You don't have a lot of fuel demand under those conditions but you do have a lot of engine vacuum. If the condition appeared at higher demand conditions it is more likely to be a fuel delivery problem. Freeze frame may show what I need to know. 

When you look at freeze frame data, look that the data applies to the code you are diagnosing. Also, don't get caught up in data that means nothing. You only need a few relevant items. 

We have a light load at lower rpms on a cold engine and a LOT of fuel being added to the mix by the computer via fuel trims. 

When you put this combination together, the lean code, the high fuel trims, the cold engine vacuum leak at low demand................... you think there may be a vacuum leak under the intake manifold. It is very common for the seals under the intake to draw up (shrink) a bit when cold and allow air to be drawn in. As the engine warms the seals usually expand and return to normal sealing. To verify, I pulled up short term fuel trim as a data item and graphed it. I took a can of my favorite, Berryman's Spray Carb cleaner and sprayed a little at the base of the intake ports while the engine idled. If the spray was drawn in then I had a vacuum leak at the seals. A quick way to see if this happened is to watch the fuel trim. If the cleaner was pulled into the intake the car would react as though it was more fuel and take fuel away from the mix. A quick negative fuel trim. Like this:

The cause of the P0171 then is bad intake manifold seals. It was a lean fuel system code. It wasn't a bad intake manifold seal code. You have to trace things to the problem with logic and testing. Whats up next? Graphing maybe?

Kenneth Hayes

G&G Auto Repair

MIL or Check Engine Lamp Testing pt.1

The Check Engine Light is on. Why? Lets start at the beginning. Your Check Engine Light, Malfunction Indicator Lamp or whatever name yours goes by currently is actually just a small bulb in the instrument panel. We are going to call it the MIL. When your car is running positive voltage is at the MIL feed circuit. I've made an extremely sophisticated mock-up to refer to.

Depending on make, model and design, the MIL will come on when you turn on the key and maybe stay on a few seconds when first started. Those are bulb tests so you can see that the bulb does work. If the MIL stays on while running or comes on while driving there is a problem. It could be a short on the ground circuit but that is very very rare. It will usually be because the computer has detected a problem. The computer will either ground the circuit directly, or request another computer to ground the circuit, again depending on the particular system. Next then is to determine if the computer sees a reason to turn on the MIL and what that reason might be. This is when a code reader comes into the picture. When the computer determines there is a problem it is not only supposed to turn on the MIL but it is also supposed to store a trouble code related to the problem. 

There are basically two diagnostic systems built in to the MIL systems. There is a federal government mandated OBDII compliant and an OEM (manufacturer) system. OBDII readers are very common and usually not expensive. When you go to a parts store and get codes read, it is usually an OBDII reader. More expensive readers and scan tools can usually read both OEM and OBDII. It depends. There are a lot of diagnostic systems out there and a lot of testers. Over the years I've used and purchased several. So let me introduce you to my little friends. 

I have an AutoXray EZ-Scan 6000 that I've had for years. It does OEM checks on old OBDI systems up to 1995. Rare usage these days for that but it does still work as an OBDII generic reader. Here is a 2002 Taurus with MIL on and the stored code. I'll get into freeze frame and data later. For now, generic OBDII codes.

AutoXRay EZ-Scan 6000

An old OTC Genisys 2.0. Just using OBDII generic here as well. 

OTC EVO Genisys 5.0 & 4.0

Snap-on Solus Pro, Ultra and Edge

OTC Encore

Actron AutoScanner Plus (older and later models)

NGS MachII

OTC Monitor 4000Enhanced

Innova 3110

Alldata Mobile (tablet)

Actron U-Scan

You might have noticed all the codes were pulled from the same vehicle using each of these code readers. You might be wondering why I would have 15 different tools to check for codes. I don't really. I have 18, but was only using the ones that would pull generic OBDII codes from this particular car. Some do more tasks, some do less. Some are very expensive, some are much less so. Some are latest updates, some are better for older cars. Some are for quick basic code reads, some for more extensive testing. Remember that the cars have more than generic OBDII codes and systems.
An automobile manufacturer tool is fully capable of doing many many sorts of tests, commands and updates for a particular make of car but in the general repair shop and aftermarket we usually see many different automobiles and to be loss costly it makes sense to go with aftermarket tools.
This OTC Encore can run Ford OEM self tests.

There are also tests that may not be available on one aftermarket tool, yet present on another. You have to use the strengths of each available tool to help in the diagnostics. When you are using a generic code reader you should be aware that you may not be seeing all the stored codes. There may be OEM system codes that don't show on the OBDII reader. Good to remember if you have an MIL on but show no codes on your reader. A look at OEM codes may reveal stored codes. Also, there are many "sources" that make it seem as though all you need is codes read and immediately know what is wrong with your car. That isn't true at all. When I try to explain there is no machine that tells you what is wrong I don't always feel like I am believed. I think often the person I'm talking to just figures I must not have one. There is a LOT of false information out there so I can understand it being confusing.
So just how useful is this P0136 OBDII code? It gives a starting point. The brief code definition given by the reader says O2 Sensor Circuit Bank 1 Sensor 2. An in-line engine design has all cylinders in a single row on the engine block. As far as "bank" there would only be one. On this Taurus 3.0 we grabbed codes from though it is a V-type block. There are two banks of cylinders. Bank 1 would be the side with cylinder #1. Bank 2 would be the other side.

Bank 1 on the Taurus then is the bank nearest the firewall. The code is for bank 1 and sensor 2. The sensors are numbered as they come from the engine exhaust manifold. Bank 1 sensor 1 would be the first O2 sensor in the exhaust of bank 1. Bank 1 sensor 2 would be the second sensor in that banks exhaust. Sensors in front of the catalytic converter are usually for fuel control and sensors after the cat are cat monitor sensors.  

P0136 then indicates a problem with the catalyst monitor O2 on bank 1. B1S2. Since the post converter sensor isn't for fuel control there will probably not be a performance problem. The post converter sensor lets the computer "see" how well the converter is working, or how poorly. When the cats getting warmed up and are doing their job you can see it by watching sensor activity. Fuel control sensors should be switching well from lean to rich at full range. Monitor sensors, not so much. Sort of a slow and less active version of the fuel controls because it is after the exhaust has gone through the converter. 

This is from a 99 Chevy P/U. Both banks and both upstream and downstream sensors. You can see the difference. 

Another from a Jeep that was in recently. You can see that the bank 1 cat is not working at all. Sensor 1 and sensor 2 on that bank are mirror images. The bank 2 cat is bad as well but working a bit. When you see a monitor running like the one in b1s2 here you will get a P0420 for poor cat efficiency. 

This one is from the same Ford we captured the code from. P0136 B1S2 Circuit Problem. 

To figure this MIL problem out we have to find out what actually sets a P0136. The code would indicate the sensor is staying near 0 volts. Ford is pretty vague on the details. But we can see in the data waveform the sensor is actually near 0 volts. 

At the most basic, if all your tool does is read codes you would need to inspect the wiring, sensor and exhaust relative to the b1s2 sensor and then monitor the signal with a meter. If the wiring, etc is good then watch the signal while feeding propane to the intake. The richer fuel should make the sensor react. If it doesn't and all else was good then you do have a bad sensor. None of that is easy or simple. Point being, a code doesn't tell you what is needed to fix. The code, when it isn't misleading, is about what needs to be tested. 

I'd like to continue this as a series. I hope it is coherent. 

To start to find out why your MIL is on you will need to check for stored trouble codes.

There are OBDII self diagnostics and there are OEM self diagnostics.

You can start with a basic OBDII code reader.

You may need more to do useful testing.

I think the next level up from OBDII code reading only would be OBDII freeze frame data. Hope to cover that next. 

Thanks for reading!

Kenneth Hayes

G&G Auto Repair

2002 Taurus: Overheating?

Came in to work this morning to find a 2002 Ford Taurus SES parked along with a note. Overheating problem, it says. To get started on the diagnosis I drove the car into the shop. The A/C was on when I started the car. The cooling fans should be running with A/C so seemed like a good time to check the fans can work. The fan motors are both running so no problem with fan motors themselves.
Next would be a look around under the hood for anything obviously a problem such as coolant leak, sensor wiring frayed, disconnected or shorted. Most obvious is the coolant reservoir is not full.

Next, top off the coolant level and position this car on a lift. Because gravity is not a suggestion, it's the law. I'm going to pressure test the system and look for leaks. That will include looking in areas more easily seen from below. On starting the engine to move the car, I looked inside the reservoir for "turmoil". The car is not at engine temperature and has been sitting for hours so the thermostat should be closed. If I see coolant trying to come up out of that reservoir it is a sure sign of a bad head gasket. But it looks calm. 

With the car on the ready to lift when needed I want to put pressure on the system. This a 16 psi system. 

After several minutes the pressure has dropped slightly. I don't see any obvious leaks from the top and no drips underneath. Time to take a look from below after pumping it back to 16 psi. 

Leaking from under a hose, at the clamp end. Actually the clamp is most accessible from above. The clamp was slightly loose. Now the leak is fixed. I don't know about the overheating though so not finished yet. It could have been overheating due to low coolant level but there could be other problems. I have to run the car, let the thermostat open and fill to level. The cooling fans run with A/C and I saw that working but the fans also are supposed to come on when coolant temperature gets around 220F. I've checked oil for coolant contamination and did a combustion gas test at the reservoir. The system is filled, the fans come on at 215F and off at 210F. Good circulation. No signs of overheating. Time for a road test. 

Didn't see any problems from the cooling system on the road test. Customer called and said he was having boil-over and overheat at idle conditions but never at road speeds. I explained what I've found and done so far. He also said he has been working on the car and only added water to the cooling system. I need to test coolant strength after this cools enough. Then I'll give him a call back.


A few things while I'm waiting:
Water as a stand alone coolant is not good. It will cause rust and it has a lower boiling point than a 50/50 mix of water and antifreeze.
Flushing the cooling system is done as maintenance when changing coolant. If your radiator is plugged it will need replaced or removed and cleaned by rodding.
If you put a stopleak product in your cooling system, do it once. Don't keep doing it over and over and follow the directions. Mainly though, don't use a stopleak product.

The engine coolant tests as mostly water.

Drain and fill with a 50/50 mix and this car should be good to go. 

Thanks for reading

Kenneth Hayes

G&G Auto Repair