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iATN Review: Newsletter for Members
Third Quarter 2009 EditionWorld's Largest Network of Automotive Professionals
Table of Contents
Volkswagen Exp Block Take A Good Look First
How To Get Good Customers Into Your Shop
Bitten By A Fusebox
HO2S Aging, Oh, Really?
Intermittent Short Finding With A Current Probe
98 Ford Contour 2.0L Stall, Erratic Fuel Pump Relay
Late Model GM Returnless Pump

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From: Scott Brown

Welcome to the third edition of the iATN Review. The first half of 2009 is already behind us and we have all witnessed some substantial changes within our industry. While the economic conditions have been extra challenging for the automotive industry, our July poll shows some signs of improvement. Over 40% of polled members report an increase in service sales during the first half of this year, compared to the last half of 2008. For more iATN member poll results, see our poll archive page, and be sure to vote in the latest poll, which is always available on the members only home page.

We're excited to bring you this issue as it highlights some great information posted on iATN this past quarter, such as a technique for finding intermittent shorts, a failure analysis on a fuel pump, a strange anomaly with an under-hood fuse box and a nice post illustrating how to attract good customers to your business!

We hope you enjoy the iATN Review. An online version of this and past issues can be found in the resources section in the members' only area. If you have any comments or suggestions, we encourage you to provide us with feedback at

Best Regards,

Scott Brown
iATN President

Full Article

Volkswagen Exp Block Take A Good Look First
HVAC Forum
George from California

2000 Volkswagen Jetta, photo
Had a Volkswagen come in today with a refrigerant leak at the expansion block, determining it was around the liquid inlet I suspected the line.

Sure glad I had my good glasses on and took a good look at the block first before just ordering a line.

[2000 Volkswagen Jetta, Expansion Block]

Full Article

How To Get Good Customers Into Your Shop
Shop Management Forum
George from Nebraska

There have been a lot of posts recently about poor/failed marketing efforts. Most of them revolve around "price-point" marketing or marketing that appeals to less than desirable consumers.

So, what can you do?

First off, you must distinguish your shop from all the others, and don't use price to do it. ;o)

Here's a start: Avoiding the WWYD

Make your shop look different than the other shops, for openers. The public perception of most repair shops is dark, dirty and cluttered.

Take photographs of your shop and you'll suddenly see your shop like the public does, rather than your own perception (in your own mind) of your shop.

Next, you have to "sell what people want to buy". People with good jobs, driving nice cars, who are logical in their thinking don't want a $69 brake job. They're smarter than that. They also don't want "Free code reading", that's what do-it-yourselfers" want.

What they DO want is to know they won't have car trouble. So, what's the best way to market that?

Let's go back quite a few years in my own shop's history. A few Summers into my shop ownership, it seemed like many of my customers would come in for an oil change and tell me, "I'm going on a trip and want to make sure the car is OK, can you look it over good?"

Well, I sure did and made a lot of sales off that. But something finally clicked in my brain--my customers were telling me "what they wanted to buy" and that was a Vacation Inspection. Wow.

So, I made a list of all the things I could think of that were common failure items on the highway, priced it at 29 donuts and offered it to my customers. They almost all bought it without question.

At this point, I'm doing the same things I did before, but now I'm getting paid for it. In addition, it made a neat "special" I could mail out that would literally get good people to call me and bring their cars in.

This doesn't even have to be mailed, it can simply be offered by the front counter staff, or you can put up signage. Maybe signage in front of your nice clean and bright shop with all the nice cars parked out front. :o)

Many of you will email me and ask me for a copy. C'mon, quit being so lame, lazy and unimaginative. ;o)

Start a spread sheet. Down the far left column are the items listed that you check. Across the top are Good, Fair, Needs attention and Comments columns. This way items can be checked off and a short explanation given.

Here are some items you can list:
  • Road test
  • Steering
  • Shifting
  • Shock/strut performance
  • Horn
  • Cruise (yes, this can be checked at 30 mph)
  • AC vent temp____Deg. F.
  • Braking
  • Windshield washers
  • Lights
  • Upper radiator hose
  • Cooling fan operation
  • Belts
  • Obvious fluid leaks
  • Coolant condition
  • Visual inspection of battery
  • Visual inspection of battery cables
  • Battery test
  • Fluid levels:
  • Power steering
  • Coolant
  • Oil
  • Transmission
  • Washer solvent
  • Wiper blade condition
  • Alignment (based on tire wear)
  • Tire condition
  • Tire tread depth
  • Tire pressure (including spare)
  • Tie rod ends
  • Ball joints
  • CV boots
  • Obvious fluid leaks (undercar)
  • Shocks and struts
The list you develop should then be given to all your techs, so they can "approve it" or make suggestions. Talk openly about the suggestions and go out of your way to accept them. This converts it from "your list", to "their list" and they'll be much more likely to endorse the program and go along with it. Remember, most techs resist change, even when it's good. This is an important step in team-building.

Tell them it's important that the list be done in the order the work will be done, so that you're most efficient on the operation and not skipping all over the form as you're filling it out.

I've developed a cool wiper blade test: Use a damp towel and wipe the rubber blades. Good blades leave no marks, black marks indicate the rubber is breaking down.

Feel free to add items to this list and do it in a post, so this can be a group-developed list that you can all use.

Voila! You now have an item you can market that will attract a good grade of prospect, increase your sales and provide something that will make your customers feel better about their cars and you.

And---you don't have to "give away the farm" to do it.

Full Article

Bitten By A Fusebox
Technical Discussion Forum
Robert from Florida

2006 GMC Envoy, BATT/Charging/Starting photo
This vehicle is fixed. Fix was quite simple in the end, testing and logic will get you there.

It relates to Albin's adventures with an open fuse, I thought this would be a good time to post my adventure.

Complaint was "A/C blows warm intermittent". Under factory warranty, customer waiting. Verified complaint, no clutch, no cold air. Quick scan with Tech 2 shows A/C request=Yes and A/C relay=On. Testing at the Underhood Bussed Electrical Center showed A/C relay grounded and power leaving the relay. Testing at the A/C clutch found no power reaching the clutch. I decided to test the section of wire between the A/C relay and the A/C clutch.

Jumpering 12V to clutch wire

I disconnected the battery, pulled the UBEC and connected a jumper wire from battery positive to E12 clutch circuit. Still no clutch. Long story short, this wire is inside a large engine harness and part of it was not easily accessed, so I ran a new wire and the clutch engaged. Put everything back together, reconnected battery, did paperwork, went to start truck and it wouldn't crank. Turn the key, no crank.

What are your next steps and why?

Full Article

HO2S Aging, Oh, Really?
Technical Theory Forum
George from California

2005 Mercedes-Benz ML500, ECM/Inputs/Outputs scandata2005 Mercedes-Benz ML500, ECM/Inputs/Outputs waveform
HO2S aging DTC is nothing new, neither is rear HO2S' influence on pilot Lambda control. A recent case study made me thinking about those issues.

I have seen a few cases of pre-CAT HO2S aging DTCs. MB's way to detect is to use what's called Tv (not the one you watch at night.:-), it's the dwell on STFT, we have seen how this is at work when it's designed to biased slightly rich or lean. But, MB system doesn't bias that way. It's a Lambda 1.000 control, instead, it measures this Tv to determine if pre-CAT HO2S is aged enough. As those aged ones will cause larger than normal Lambda excursion.

2005 MB ML 500 came in for MIL on, not the 1st time. "George, can you figure out this?", "Let me try" ...; BTW, this vehicle is right before MB started using A/F sensors pre-CAT.

SDS short test


Okay, both banks pre-CAT HO2S are switching. They say rear HO2S can stay anywhere it feels like, right?:-) So lets say it's okay too for now.:-)

I did look at LTFT and STFT, a little strange, but no smoking guns there.


STFT with a little swing

Next, I went to look at Lambda control graphing, basically, HO2S graphing on SDS. Sorry for no color and poor resolution, the best I can show you for SDS image.


2000 rpm

Huh? Interesting. Why B1 pre-cat HO2S say it's lean biased and rear says it's rich? And completely opposite for B2?

I did verify sensor readings are correct comparing on-board and off-board, they matched. SDS guided test also mention to test HO2S heaters, I did that too.

Bx1 Heater Voltage&B1S1 Heater Current

The measurement on peak current to the heater is a little over 500mA, both banks are the same. By now, it's obvious, this is not a large Lambda excursion, but a pre-CAT HO2S and after-CAT HO2S don't agree with each other. It turned out to be a cross connected rear HO2S.

These are after "repair" testing results.

After "repair" Idle

After "repair" 2000 rpm

From this case, what I have realized. 1, Rear HO2S influence on Lambda pilot can be quite strong (I couldn't find any document in detail in MB WIS, I have to piece them together by myself, I wish I didn't have to). 2, What does it mean "delay time is too short" in DTC? I figured, it's negatively too long.:-)

Is there any other auto manufacture(s) also using these?

I didn't measure oxygen content, I wonder what it could be?:-)

Full Article

Intermittent Short Finding With A Current Probe
Technical Tips Forum
Albin from Washington

current probe finding an intermittient shortheadlight bulb limiting the current
From time to time I get vehicle in that will intermittently blow a fuse. There are several different ways to approach this problem, and since there is no one way that is the best, here is one way to approach the task.

This vehicle was a 1996 Subaru Legacy that spends a lot of it's time on gravel roads that are sort of rough. The fuse #15 blows, which shuts off the heater, radio, dash lights, and a few other things. Checking a wiring diagram of this circuit found many different branches in the circuit. I used a fused jumper that was hooked in place of the fuse, my current probe was hooked to the jumper, and the current probe hooked to my scope. After studying the wiring diagram, I decided to start looking for the problem under the dash. I find that many times, the best way to look for problems like this, that are burried under things is to use my fist, and start pounding things. A few light whacks to the dash, around the instrument cluster found this happening on the scope [current probe finding an intermittient short] Now I know the general direction of the problem. Many times when you start on a project like this and you move a wiring harness, the short to ground is gone, and is real hard to find again. This one reason that I like to use this process. when I started to remove the instrument cluster, the fuse blew. Now it's on to step 2 of the process. I keep an old glass sealed beam headlight with jumper wires soldered to it for just such occasions. The headlight will limit the current to the circuit, and if the circuit is shorted, it will light the light bulb, so, with the headlight hooked in place of the fuse, [headlight bulb limiting the current] with my current probe on one of the leads, I started moving things, and in a few minutes I had the cluster out, and had found where a harness had rubbed on a steel brace that was inside of the dash. The only visible imperfection I could see on the harness was where the outer covering of the harness was a little but rough. Moving the covering around I found a very tiny spot rubbed in one wire which was the culprit. A short piece of heater hose and a few plastic tie wraps fixed the problem.

Full Article

98 Ford Contour 2.0L Stall, Erratic Fuel Pump Relay
Ford Driveability
Brian from Washington

Intermittant stalling associated with erratic Fuel pump relay activity. Sounds like Morse code. Tried swapping out FP relay and PCM relay during failure with no improvement. Normally with KOEO, fuel pump will only run appx 1 second when key is turned on, unless cranking or running, but this erattic relay condition can last for minutes with KOEO! Tried jiggling Ign switch thinking a possible intermittant contact issue may be causing this failure. Bypassed direct bat + to fuse #14 output circut direct to fuel pump and pump would then run normally, but still erratic FP relay condition continued. When in failure mode, voltege at fuel pump was varying as expected from 0 - 12 volts in sync with erratic FP relay activity. Charging / battery system tests all normal. Checked PCM grounds, Battery connections and all accessable related grounds, which all appeared clean and tight. Remoced PCM and inspected connector pins = OK. Recently had MAF and throttle plate cleaned by others. System does not have the FRP (fuel rail pressure sensor). MIL on when arrived at shop. Codes found PO231 , P0500, P1703. Cleared codes and none re-appeared after recent failre event except the P1703 (brake switch). NOTE: may be of interest. Code P1703 brake input failure...scan tool test revealed PCM not recognising Brake switch on/off, though brake lamps work, as does the trans interlock solenoid. The P0500 VSS code was in the historical codes but vehicle speed reading on scan tool is normal when driving. Checked its connector = OK. Courious if anyone has ever expeirenced this weird FP relay situation and Would appreciate any pin-pointing suggestions at this point before back-probing values at PCM, hopefully in a failure mode (which unfortunately is not too often,anywhere between 5 - 112 miles lately...) one last note: KOEO self test says "no communication" thouhgt you can hear it cycling threw tests..? KOER performs normally except always gives a P1000 (incomplete test message)

I appreciate very much everyones input given. Sam from Ohio nailed it...

(You can read the full article, 5 replies, and FIX here.)

Full Article

Late Model GM Returnless Pump
Technical Theory Forum
Andrew from Utah

2006 Chevrolet Silverado 1500 LS, Fuel Supply photo2006 Chevrolet Silverado 1500 LS, Fuel Supply photo
I had the privilege of replacing and doing a failure analysis on this fuel pump. In the process I grabbed some photos to share the design with everyone. It is a returnless system with a lifetime filter in the module. It has a pretty neat jet pump setup to keep the module filled to the very end.

Here is the assembled pump. Notice the fuel pressure regulator is on the outlet side of the filter. Also note that the outlet of the regulator drops into a tube. [Assembled Pump] That tube is a part of the jet pump setup. [Jet pump tubes]  On the bottom of the module there is a jet pump inlet which sucks fuel up the other tube and into the module. On the left tube it is open to the bottom of the tank. The right tube has the 90 degree fitting that goes under the left tube and has an orifice in it that faces up. That orifice is like a high pressure nozzle that causes the fuel around it to flow upwards and into the module. [Jet pump intake]

The bottom of the module has the typical check valves that allow fuel to flow in if the fuel level in the tank is higher than the level in the module. [Check valves]

The fuel filter is pretty basic. [Fuel filter and regulator]  The top is sealed to the housing with an o-ring and the filter media is a paper/fiber composition. Fuel flows from the outside in. There is not a bypass valve of any kind should the filter become plugged. [Fuel filter insides]

The fuel pump itself is just your basic style. The strainer fits inside the module and unlike other designs there isn't a strainer outside the module. [Pump]



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