The TPMS light is on, and it is easily isolated to a nail in one of the tires. You repair the punctured tire, and air all the tires to their correct pressures. Yet the TPMS light is still on.
Not unusual. Many TPMS sensors have to be "awakened" before they will transmit their data, and there are a few different ways OEMs do that. Many will wake up at speeds over 20 MPH, so a drive around the block usually turns the light off. But there is another way. Use your TPMS tool to wake them up!
I use the Bartec 400, and have used this method to turn off the light on many models without the drive around the block. I've also used this method to retrain sensors after a tire rotation or sensor replacement, when the OE procedure calls for either letting air out or using a magnet around the valve. In those cases, though, I still had to put the vehicles into "learn" mode.
The Bartec tool is also the first tool I grab when diagnosing a TPMS light. Yeah, I know, check the tire pressures first. But what if they check OK? I have had a few rare instances where the sensor was reporting incorrectly, and the control module doesn't know whether it's being told the truth or a lie. If I read a low pressure tire, it is an easy second step to check the pressure manually to confirm the sensor reading.
It is also a good idea to test all the sensors and look for a lit TPMS light PRIOR to any tire work. It is infinitely better to identify a failed or weak sensor before the tire is broken down, than to explain to your customer afterward why the TPMS light is on when it wasn't on before.
When removing the tire, be sure to break the outer bead 180 degrees away from the sensor to avoid damage. Then remove the locknut and seal, allowing the sensor to fall into the tire. Remove the sensor and then remove the tire. Install the sensor last, and use new seals and lock nuts. They don't require a lot of torque, so be careful. There are special tools available to insure proper torque. Use them.
The valves inside the sensor are special as well. Don't exchange one from a rubber stem for use in a TPMS sensor.
Last tip...don't use tire sealer in a TPMS equipped rim. If your customer did, replace the sensor...it's garbage once that sealant gets into the sensor air inlet.
Whew....that was a bit more than I originally intended. Oh well, I've been told that sometimes I don't know when to shut up!
The AutoPro Workshop was just a dream a little over a year ago, and has grown tremendously. That makes staying in touch with your favorites a little harder, with more and more media added to the site daily. So here's a tip...add your favorite writers/contributors as an RSS feed,
It's easy to do. Just scroll down to the link on their profile, or the one near the bottom of their latest blog or media addition.
That way, you'll know when new stuff is added...whether it shows on your home page or not!
And thanks for making the AutoPro Workshop the friendly online community it is!
Fuel flow and injector faults can result in drivability problems. Some OEM scan tools, as well as some high end aftermarket tools, allow you to perform power balance and/or injector balance tests on those OEs that support such a test. Injector balance can also be done using a tool that fires the injectors individually while you measure the drop with your fuel pressure tester, but this can be a time consuming task. There is another way to check this flow, and it uses a DSO and a special pressure transducer.
I've used the SenX FirstLook transducer for many tests involving low pressure or vacuum pulses, and have shared those tests here in the past. Today, I'd like to share another product from SenX...the ES300 Fuel Pressure transducer.
This tool connects to the fuel rail at the supplied Schrader valve. It also comes with an adaptor that allows it to be connected to vehicles without a Schrader, using the quick disconnect coupling common to many professional fuel injection pressure testers. With the ES300 connected, the next step is to bleed any air out of the sensor much like you would your fuel pressure gauge, and then connect the sensor to the scope and running the engine. (The tool will work with any DSO, and comes with both BNC and banana fittings).
Here's what a raw pattern might look like. This one is taken from a 2003 Dodge Dakota with a 4.7 liter V8 with over 90,000 miles on the clock and no drivability complaints.
This pattern is created by the changes in pressure in the fuel rail. The theory is if all injectors are functioning normally and flowing correctly, the pattern should be repetitive and uniform. On this capture, the blue trace is taken from the #1 injector, and the firing order is 1-8-4-3-6-5-7-2. Using that information, I saved the screen capture and used Microsoft "Paint" to mark of the individual injector firing times. I also color coded the events to show the cylinders on bank one (cylinders 1-3-5-7) and bank two (cylinders 2-4-6-8). The connection point for the transducer is directly to the fuel rail Schrader valve, located on the right bank fuel rail between cylinders 4 and 6.
The ES300 creates a positive voltage during a DROP in pressure, so the peaks you see here are just that...the pressure drop across each injector as it fires. In this capture, the peaks are all reaching about the same level, indicating the injector flow rate is pretty even. However, notice the small variances in each wave. Some have two peaks, some don't. The ones with the distinct "double peaks" are on the same side of the engine, and this may be caused by the proximity of the sensor...it's closer, so the signals are dampened less than those on the left bank. It may also indicate that the injectors are dirty. I haven't had a chance yet to capture before and after patterns.
What happens when we remove an injector?
Can you tell which one I unplugged? Remember, positive peaks indicate a drop in pressure.
That's right...it's #5. Notice that there is no drop in pressure on this cylinder. Because the injector did not open, fuel rail pressure rose slightly higher than normal and caused a higher pressure drop when the next injector in line fired, then the pattern returns a more normal level. If diagnosing a misfire, I would instantly know where to narrow my focus. Just keep in mind, that low flow or no flow can be caused by both a mechanical fault and an electrical one. Ideally, I could monitor injector current, voltage and pressure change...all on one screen. You can also test the injectors under different conditions when looking for a fuel flow issue, comparing idle to a power braking 1500 rpm pattern.
As with any diagnostic technique, it alone is not conclusive. It is, however, a worthwhile addition to your diagnostic arsenal and can save you valuable diagnostic time over manually testing injector flow.
"Pete, I need you to find out what is making the whistling noise on this Town and Country. It sounds like its coming from the rear, and the only thing I saw was what looks like a deformation on the rear hatch seal. I've already moved the luggage tracks around...I don't think that's it."
So it began.
I checked the seal my service manager thought was deformed, and compared it to a few other Chrysler minis we had on the lot. The deformation, as he put it, was normal, but I did find that the secondary seal that deflects water away from the wiring harnesses was missing. Perhaps that was the noise as well. I ordered and installed the seal, then went on my first test drive. (Remember that for later...I did say FIRST).
The whistle was still there, beginning just over 45 MPH, but it sure sounded like it was coming from the center of the windshield to me. I got back to the shop, grabbed my flashlight and masking tape, and started looking around for a cause. The first thing I noticed was the position of the luggage rails. The rail supports are marked all along their length every few inches with a single hashmark. This allows the owner to make sure they are both square to the car. However, there are two sections where the hashmarks are doubled, and that usually means that is where the rails should be when not in use. The factory already knows they can cause noise, and these marks indicate the spots where the noise is minimal or eliminated. I moved the front and rear rails to their respective marks, locked them down, and test drove the van again.
Still there.
OK, how about the seals? Door seals, glass seals, side mirror seals, windshield seals...all were suspect. I drove the car again and again at speed, and started altering things I could to see if the noise would change. First, crack the door open...nope, noise is still there. Roll both windows down, one at a time. Nope, that isn't it. Have an assistant crack the passenger door open. Still there. Alter the mirror positions. Nada.
I taped off doors, mirrors, the cowl vents...and more. Still whistling...
Turn the windshield wipers on...BINGO! The whistle stops and starts in synch with the wipers. That means that the wipers are disrupting the air flow over whatever is causing the noise. That only leaves the windshield, so out comes the masking tape and I tape it all off. I think the next test drive will confirm the cause, and I'm excited...I've spent way too much time on this thing already.
Nope...that ain't it...darn (expletives deleted for the sake of our viewing audience).
What else could it be? I stood back from the van, trying to envision what the airflow would look like. The luggage racks were all I could see, so I looked closer. There were caps on the front of each, and water drain holes at the base of each, so I taped those off. Still whistling. I compared the rack to others on the lot, but the rack design was different from the others. The one thing that caught my eye, though, was the solid cross members used on them. Looking from the top, I saw an open groove running the length of both racks on the whistler. I at first thought they were supposed to be there, perhaps to be used as an attachment point for holddowns when loaded, but maybe they weren't supposed to be open. What if there was supposed to be a trim peice sealing those openings? Out came the tape....it was worth a shot...
EUREKA!!!!
Sure enough, the whistle was gone. My boss had heard the noise in the rear, but had moved the racks around after finding both positioned near the back of the car. I heard it in the front, because the forward rack was now at the front. (Of course, I learned this valuable bit of information AFTER I had found the noise's source!)
The trim is not available separately and our customer was not excited at the prospect of buying new cross members, so I came up with a different solution. The space I needed to fill was just under 1/2" across and 1/2" deep. A 5/16" ID fuel line was a perfect fit in the spacing, and looked almost OE. With the lines in place, and one more test drive to be sure, the whistling was finally silenced!
It's no secret that I think a scope is a worthy addition to any tech's diagnostic arsenal. And there are several very good ones available today.
I currently own a PICO 3443, and recently had a chance to try out their BETA diagnostic software some more. This is their battery/starting/charging test screen:
The procedure is easy enough. Connect channel 1 to the battery, and wrap your 600 amp current clamp around either battery cable, connected to channel 2. Use the options menu to set the CCA rating for the battery, adjust for ambient temperature, and key the Start button on the screen. Then start the car. The software will collect data until it has what it needs to analyze everything, then spits out the results. Here's a close up view of some of the test results it lists:
The only fault I saw off the bat was the lowest voltage recorded. This is a known issue, and is a result of the sheer speed of the scope. The same is true of the maximum current reading. Here, the scope is catching that momentary high current the starter needs to start turning. This is not the same as the starter draw you typically measure...the draw required to keep the starter turning once it is moving. However, the data is just above the results and it is easy enough to see what the loaded voltage and average starter draw was for yourself. In addition to the list shown, the test lists AC ripple measured and more, providing a quick picture in about 60 seconds. And the final report can be printed out to share with your customer and/or keep in their files for future reference.
Last weekend, the family and I went to check out the car show at the Tampa Convention Center. Located in downtown Tampa in the Channelside area, the center is located in one of Tampa's hottest entertainment districts. There is no particular order to the photos, and no captions...I published it strictly for your viewing pleasure! Enjoy!
I recently read a neat tip posted by Jeremy Mindes, owner of Sidejob Auto Repair in West Jordan, Utah. With his permission, allow me to share it with all of you.
Diagnosing a leaking head gasket can be tough on some cars, especially if the leak isn't that bad. There are block testers that use a chemical reaction to indicate a leak, some use their exhaust gas analyzers to sniff out combustion gasses in the coolant, and of course many are easily found using conventional pressure testing techniques. Our own Richard McCuistian recently posted this video sharing yet another method techs can use when diagnosing these problems:
http://workshop.search-autoparts.com/_Lots-of-ways-head-gaskets-can-blow/video/796165/31710.html
But Jeremy had a novel thought...how about using one of those home CO detectors if you don't own a 5-gas?
The cost of the unit is roughly $40, and Jeremy uses his spill free funnel to hold the unit over the running, open radiator fill. He then wraps a plastic bag over the top of the funnel and seals it around the base to keep the gasses in. According to Jeremy, the unit is loud enough to hear over the running engine. But, he admits, he has only used this technique once and wants to try it out again on the next suspect gasket.
This is a neat idea, and adds yet one more potential method of verifying a failed seal. If you've tried a similar method, or decide to try Jeremy's for yourself, be sure to share with the rest of us the results of your experiments. This is how new testing methods are born...for the benefit of us all.
Thanks, Jeremy, for allowing me to share this with our members and readers!
This car came in on a hook after dying on the customer while driving. One of my fellow techs was assigned the car and proceeded to check it out. Engine spins over normally, battery appears healthy. Adding a little carb clean to the intake, he tried to see if it was a fuel issue or something else. Car still didn't start. A little more digging and he found no spark or injector pulse while cranking.
Do you know what's wrong yet?
Codes were pulled, and he found several...CKP sensor circuit fault, CMP sensor circuit fault, BARO sensor circuit fault and TPS sensor circuit fault. He figured that it had to be a CKP issue, so he ordered one and installed it later that afternoon.
Would you have done the same thing?
Still didn't start.
He came over to ask for help, so the first thing I did was check for related TSBs. While I've found several cases where the answer was already waiting for me, I didn't find any clues this time. Specifically, I was looking for any TSB that related to what all these sensors shared in common...a 5 volt reference fed them by the PCM. My next step was to check in my other resources...IATN and Identifix. I found several references here to failed CKP sensors shorting out the 5 volt line, and a few for PCMs that quit supplying it.
I printed out the engine schematics so I could identify all the sensors that shared the reference line, and grabbed my DMM. The TPS is one of the easier sensors to reach, so I checked for the 5 volt reference there and measured only 0.31 volts. I know the problem, now to find out what's causing it. I unplug the TPS connector and the voltage remains the same. OK, that's not it.
The next closest sensor is the MAP sensor on the left side of the intake. Unplugging the sensor restored the 5 volts at the TPS, and the shorted sensor is located. To verify, I started the car...no problem, started just fine.
All this took a total of 20 minutes from the time the tech first asked for help. I don't say this to brag...Lord knows I still have a lot to learn and make more than my share of mistakes...but to illustrate a point I've made before. This business requires continuing education. If you as a tech rely on what you already know, and don't try to keep learning, technology is going to pass you by. Reference voltages aren't new and neither is their diagnosis. How do you think this tech would handle a bus failure on a CAN system?
Knowledge is power...earning power. Keep on learning!
We've been seeing more than a few Explorers with broken recirculation (fresh air inlet) doors. The door breaks at the crank pin and falls flat on top of the blower motor inlet, reducing air flow to the cabin and reducing the ability of the A/C system to cool the passengers in the process. This is for the later model Explorers that have the evaporator behind the dash instead of the older models that had the case under the hood.
The procedure is to remove the evaporator case from the vehicle to replace the assembly. This requires removing the dash, and trying to access a few hard to reach bolts. The lines leading to the evaporator are not the easiest to get to either, so avoiding their removal would be a good thing.
Here's a way to do it with the evap case left in the car...
Remove the dash to gain access to the fresh air box, located on top of the blower motor. If you use an OEM replacement like I do, you'll get the whole assembly. It's held on to the HVAC housing by only three screws, but two of them are on the firewall side and barely visible. On the old unit, you'll see a grill cast into the plastic on the cabin side and firewall side of the box. Using a pair of cutters, cut out both grills from the old unit and remove. Now you can reach in and remove the broken door. Next, on the firewall side of the box, remove the foam insulation sealing the box to the inlet. From the engine side, remove the two right side nuts that secure the EVAP case to the firewall. This will allow enough movement in the case to reach in through the old box and remove those two back screws. For extra movement, remove a third nut securing the case...located to the right of the A/C lines.
Install the new box, and gently pull back on the case to reach in and install the two back screws. This will be a tight fit, but a little patience will be rewarded. An 8mm gear wrench works great for tightening them.
Now reassemble! You've replaced the failed part, and didn't loose any refrigerant or coolant, and didn't have to fight that left most case nut that is hidden behind the engine!
Hey all!
This is all done in fun, but does make the case for the need for bettery consumer education. I have met more than one customer, as I'm sure you have, that would be this easy to take advantage of. The reverse side is that I've also been in shops that would do just that, but that is another issue, isn't it?
Want to make a difference? Offer clinics in your shop to your community or offer to speak to community groups, like the Rotary, Women's Club, even youth groups like the Boy and Girl Scouts.
Enjoy!
This video was posted on another site by a friend, and I thought it was appropriate to share it here. Hope you get a giggle out of it!
As techs, we often have to reach into the bowels of the engine compartment, sometimes on engines that are still hot. Over the last 30+ years, I've gotten my share of cuts, burns, and bruises from forcing my hands and arms into places they really weren't designed to go. A tip I learned way back helps minimze the damage at very little cost.
Take an old pair of athletic socks...you know, "tube" socks...and cut the toe end off. Pull the sock over your forearm to help protect it from heat, scrapes and greasy parts.
You might look silly to your fellow techs, but your body will appreciate the attention to prevention!
Or maybe mice, squirrels, chipmunks...I don't really know for sure...
This Honda came in for a routine oil change, and while inspecting the vehicle I noticed that the windshield washers didn't work. Not unusual for my area, and typically all it needs is some washer fluid added to an empty reservoir. Not this time. Still no fluid, and I couldn't hear the pump running from inside the car.
Took the line going to the nozzles loose to see if anthing came out there...nope, the pump is definitely not running. The pump connector is not the easiest to access from the top of the engine compartment, so I figured I'd check the fuses first. I grabbed my PowerProbe 3 and hooked it up to the batterty, turned the key on and removed the access panel to the underdash fuse block.
The PP3 makes checking fuses quick and easy, with it's illuminated tip and audible tone. Great for cramped areas where actually seeing the meter reading isn't critical. All the fuses checked OK...on to the pump connector.
With a little effort, and laying on my back, I disconnected the connector and repositioned it so I could reach it from up top. Power is supplied with the key "on", and the control is on the ground side, completing that side of the circuit to actually turn the pump on. I measured voltage with the PP3 at the power feed and saw this;
No reading whatsoever on the built in voltage display. This can only mean one thing...an open circuit on the power side. Moving over to the ground lead gave the same display. But this car has less than 25,000 miles on it and looks very clean. Unusual to see a problem with the wiring on a Honda of this young age...
Looking along the harness to see if there were any obvious visuall clues, i followed it along to its mating with a main harness and saw it heading back towards the firewall at the right rear corner of the engine compartment. This spot was a little hard to see (and harder to reach) as both the cruise control linkage and brake HCU are located there. But with a good light, I could make out the most likely cause of the open path:
Not an every day thing, but occurring often enough that I'm not surprised by it anymore, some critter was obvously nesting in the compartment. It had used some of the firewall insulation to line its nest, and with the debris removed the harness damage was exposed. Luckily, not too bad, but it would take some time to get to and repair properly. The customer returns next week to have it done...
