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iATN Review: Newsletter for Members
Second Quarter 2011 EditionWorld's Largest Network of Automotive Professionals
Table of Contents
iATN Polls Show Signs of Business Improvement
Ford & L/M Parts On-Line
Draw Test Using Voltage Drop
2011 Cruze Silver Bullet
GM Ignition Lock Cylinder Removal Tips
What Does a PassKey-II 'Fuel Enable' Signal Look Like?
Used Chrysler PCMs
No You Can't Use The O2 Sensors To Judge A Cat

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iATN Polls Show Signs of Business Improvement
Scott Brown

Welcome to the iATN Review, which highlights some of the highly-rated content posted by members on iATN. Twenty eleven is now out of the gate and, for most, it appears that the service and repair industry is beginning to show signs of improvement. We recently concluded a poll asking how overall business fared in comparison to previous years. The 2010 results indicates 41% of participating iATN members had an increase in business in 2010 compared to 2009.

These results show a positive trend continuing, compared to both the 2009 and 2008 results, which indicated that 32% and 27% of those participating in the poll had an increase in those years, respectively. And for the (still large) segment of our members pushing through the down-turn, there are signs of overall improvement. While 30% of participating members indicated business was off significantly in 2008 and 2009, this number was down to 21% in the most recent poll. While these polls are not scientific, they are insightful -- and encouraging -- when compared to each other, year over year.

In this issue of the Review, we have some really interesting member-driven articles, including a tip on online parts ordering through Ford & Lincoln Mercury, a "heads-up" on an engine performance issue with one of GM's very popular vehicles, an anti-theft visual into the Passkey-II "Fuel Enable" signal, and some very good discussions on OBDII catalytic converter performance analysis.

We hope you enjoy this issue, and if you've missed any, you can access the previous issues here.

Best Regards,



Scott Brown
iATN President

Full Article


Ford & L/M Parts On-Line
Shop Management Forum
Rusty from Massachusetts

We had a thread running recently about parts ordering screw-ups. I commented that at our shop each of us looks up our own parts or makes the calls ourselves to minimize the wrong parts sitiations. All of our aftermarket suppliers have on-line ordering and we probably order 70+% of our stuff on line. I've been using Honda's and Toyota's on-line look up for a while now to avoid the "exploded-view diagram fax dance".

On the referenced thread I made this post regarding Fordparts.com.

I've been using it for a few days now and find it helpful as long as you get hooked up with a Certified Parts Wholesaling Dealer and get their parts manager to set you up with "sponsorship". Once you're sponsored and given an invitation code, you can open up Ford Catalog Advantage (FCA) for free. These same dealers can also provide free log-ins to Fordinstallersupport.com which gets you OASIS and TRC (the actual dealer service info site). Many parts managers have no clue about this free offering.

I found that getting familiar with FCA wasn't a big deal. So far, I'm not thrilled with the VIN filtering but you can find the correct part # easily. You'll need a cooperative parts manager if you're his first sponsor as it is a tad complicated on both ends. Once set up, you can look up either on Fordparts.com or jump to FCA and get better info and select the part from that site. Once you move the item into your "cart" it gets plunked into your Fordparts.com cart where you can check availability and finalize the order. That part needs some tweaking IMO.

Full Article


Draw Test Using Voltage Drop
Technical Tips Forum
Harvey from California

I had a car in today that would have a dead battery after sitting for a couple nights. Checking for a draw I found it had a 220 ma draw and was going to start with the usual pulling fuses and checking my Amp meter. One of the other techs brought over the February 2011 edition of Motor Age and told me to read an article and see if it works. I did and it did. I don't remember the title of the article but I can get it if anyone is interested.

The article went on to say that basically, everything has a resistance value and if there is current flow and you can measure on each side of it, there will be a voltage drop. It said to check for a voltage drop between the 2 exposed tabs of the fuses. So, setting my D.V.O.M. to the mv scale I proceeded to do a voltage drop test on all the fuses under the hood. When I got to the last 2 (of course) they each showed a .4 or .04mv drop, can't remember exactly but all the others were 0mv. They were the fuses for the headlights (low beam right and left).

Now, If I had done the old pull a fuse, see no change in the system draw, put the fuse back in, then neither one of those fuses would have shown a reduction in the system draw due to the way the circuit is wired and the location of the problem.

Had I done the pull a fuse and leave it out then pull the next and leave it out, etc etc etc... I may have been looking in the wrong location thinking it was just the circuit pertaining to whichever headlight fuse was pulled last.

Not all of the fuses will be 0mv as there may be some current flow at the fuses that power clocks and or modules but those fuses should have a very small voltage drop. It (the article) also stated you can find the amount of current draw if you know the resistance of the fuse in question. Doing the voltage drop way you are also not disconnecting power to module which could wake it back up when re-installing the fuse and possibly spiking the current draw, popping the fuse in your meter or making you wait for the module to go back to sleep.

For my first test using this method, I can say it worked much better than my old methods so I thought I would pass it on.

Full Article


2011 Cruze Silver Bullet
Technical Tips Forum
James from Florida

In the past month, I've seen 3 Cruzes with the same problem. All had the LUW 1.8 engine and from 800 to 1200 miles. They come in with a complaint of MIL on, rough running, and black smoke out exhaust. They always set a P0101 and sometimes rich and/or misfire codes.

In each case, if you graph MAF on GDS2 between 1.0 and 4.0 gps, at idle with all accessories off, the MAF will usually run about 3.2 - 3.8 gps with a constant .5 gps change. The graph almost looks like a perfect sine wave. The MAF is over-reporting air flow to the ECM.

If you remove the top of the air filter box, there is a short piece of tubing with a screen on the end made out of plastic. This acts as an air flow straightener/diffuser for the MAF. This tubing falls out of the air box cover and lies on top of the air filter. This exposes the MAF to turbulant air flow. The retention on this tube is poor and I have been cementing them in place with hot melt adhesive. After the repair, the MAF idles at about 2.4 - 2.5 gps with almost a straight line graph.

If you're a G.M. tech, keep an eye out for this.

Full Article


GM Ignition Lock Cylinder Removal Tips
Technical Tips Forum
James from Florida

impala lock cylinder with trim bezellock cylinder housing relationship
I have recently been blessed with two different GM vehicles with the dreaded no turn stuck in the off position and needing a new lock cylinder. The two that I ran into had keys that were unworn and gave no indication to the owners of an upcoming issue. The two vehicles were a 2005 Avalanche and a 2004 Impala.

Here are some of my tips that worked for both units allowing me the ease to rotate and install new cylinders. The first steps involve pulling the covers off the key lock cylinder on the exterior where the key enters the lock, this also requires pulling the upper and lower covers on the Avalanche, and removing the dash face on the impala.

The next step is to use a pair of long handle side cutting pliers my choice is Snap-On 312cp. I use these to cut the exterior face flashing off, this is the area the plastic or black cover snaps onto. Once this is cut away, you can see the area where the lock bar gets stuck in the housing not allowing it to rotate to the on position which is where it needs to be to remove the housing from the column/dash mount. As long as you have a key that belongs in the cylinder the next step is to put the key in the lock cylinder. Get a cotter pin and straighten it, I believe that a 3/32 is what I used. After straightening it insert the flat portion into the gap between the lock bar and the housing grove and push gently into the housing.

This effectively is pushing the lock bar back to the retracted state that should normally occur when the key is inserted into the tumblers. Once it is inserted try to rotate the key, this sometimes requires a few attempts but was very effective for me and allows you to salvage the tumblers so that the new lock cylinder can be keyed using the codes from the old tumblers since no damage is done from drills etc.

It worked great for me twice so give it a try. It may not work for all but for me I'll try it every time before I touch a drill.


Full Article


What Does a PassKey-II 'Fuel Enable' Signal Look Like?
Technical Tips Forum
Mohammad from Illinois

1996 Chevrolet Monte Carlo Z34, ECM/Inputs/Outputs Drawing1996 Chevrolet Monte Carlo Z34, ECM/Inputs/Outputs Waveform
We know when a PassKey-II Decoder Module does recognize the key pellet and finds it to be the right one (meaning the match up is OK), it will enable the starter relay and send an enable signal to PCM to power up the fuel pump relay and the injectors. We also know enabling the starter relay is accomplished simply by pulling down one side of the relay's control coil (Figure-1) [1996 Chevrolet Monte Carlo Z34, ECM/Inputs/Outputs Drawing] . But I never knew what the fuel enable signal to the PCM looked like. This post is about that, if you know it, no need to read on any further.

We had this 1996 basket case Monte Carlo (3.4L) that came on the hook for a no-crank, no-start problem. A little more questioning of the owner revealed that a security system that might or might not have had a remote start feature was installed on this car for years, and since they have no key fob of any sort, best is, he suggested, to have it disconnected to see what else was wrong...if any! We were also informed about the customer's budgetary restrictions, pending divorce, lost dog, leaking roof, ailing grandma, etc!!!

The fact that the car has been sitting for a year and a half in their driveway was not something that was mentioned at all, that came out a few days later as an added bonus when I demanded additional information and/or a little more truth.

About a bucket load of wires, modules, relays and Scotch-lock connectors that constituted the bulk of the add-on system were removed and the car was wired up to it original shape as best as possible. The battery was charged, and then the engine cranked but would not start. Fuel pressure was checked to be zero, and when the fuel pump relay was manually activated, the fuel pressure came up reasonably well. So the PCM was not enabling the fuel pump relay. The security light was of no help because it was out, either taken out or had a blown bulb. So the question now was do we have or have not a security issue?

Well, to figure this out quickly, we disconnected the 2-wire connector under the column (the one that goes to ignition lock cylinder) and then, the starter did not crank!

I concluded this means the Decoder Module is recognizing the key's resistance, that's why it does not crank without it, but, do we have a fuel enable signal? What it is and how it looks like?

Well, MOD (in my case...the worn 1996 Mitchell Manual) said to check for a 5V reference voltage at the Pin #A3 of the Decoder Module's plug, with the plug disconnected and ignition switch on. There was no 5V to speak of; best value read was 0.55V...not enough.

So...we pulled the PCM out from the cavity around right front wheel well by clearing a few odds and ends like a junction block, radiator overflow bottle, body braces, covers...etc. A mouse nest larger than the size of a baseball was also found under the PCM but no sign of critters chewing out any wires.

With the connectors still on PCM, Pin #55 of the C-1 was checked along with the continuity from this pin to A-3 of the Decoder Module plug, still no sign of 5V, but continuity was intact. The conclusion was that we had a PCM!

Luckily, my friendly local salvage yard had a PCM that was close enough (!), meaning the service number was within a digit or two of the original. I know this is not good enough and not exact...but for the car on hand, it seemed good enough. So I gave it a try.

Our used PCM started the engine! After a few nerve-wracking knocks, it smoothed out and surprisingly run well for a car that had sat for year and a half. All warning lights went off…and it seemed to be running fine anytime we started it and allowed it to warm up.

Since the PCM was still hanging there by the wires, I decided to see what actually the fuel enable signal looks like. Well, on key up, it shoots up to 5V and once module starts enabling (!), it changes into a pulse-train as shown on Figure 2. [1996 Chevrolet Monte Carlo Z34, ECM/Inputs/Outputs Waveform]

While the engine is running, it maintains the pulse-train of the previous capture and remains as such (Figure-3) [1996 Chevrolet Monte Carlo Z34, ECM/Inputs/Outputs Waveform] ...and I assume (watch out!) as long as it stays in that state, the fuel pump/injectors are activated and the engine keeps running. I do believe this is the 2.5 V that is the step Mitchell says to check for if the 5V is present.

I am not sure whether the specific of this signal (pulse-width, frequency, etc.) is/was particular to this car/engine, VIN, or is a Decoder Module's feature, or is something general to all cars of this vintage Pass-key-II. I am assuming (here I go again) the latter, and am thinking perhaps this is what the add-on remote start people do to fool the PCM. That is put a signal generator device in this line which makes the PCM think the Decoder means "Enable". But I am not certain and I don't know.

So the car was delivered with the used PCM and all the related caveats, and the owner said he is taking it to DMV right then to get a license plate for it! Go figure.

Full Article


Used Chrysler PCMs
Technical Discussion Forum
Mike from Connecticut

There was a recent thread about programming used PCMs in Chrysler cars. I was positive that it wasn't possible with a SKIM equipped car. We have told many (used car lots usually) that it couldn'd be done. We had tried in the past and failed. Mike Marshall posted that he did it all the time. I was skeptical. BUT yesterday while trying to clear the yard for the snow storm we get a tow in from a used car lot with a used PCM. Blocking everything. I figured why not give it a try. Went into SKIM-hit replaced PCM -entered PIN and darned if it didn't take. Thanks Mike!

Full Article


No You Can't Use The O2 Sensors To Judge A Cat
Emissions Forum
John from Pennsylvania

1999 Ford F-150, Emissions Scan Data2002 Ford Explorer XLT, Emissions Scan Data
The recent thread where I had my fun at Lances expense needs some closure. First, when encountering a catalyst code there are a few things that the technician must confirm. They are in no particular order that there are simply no TSB's or software updates. If the engineers got the testing wrong and the catalyst is failing falsely, or prematurely as Rags said that is where you will have your only chance to do something about it. If the engineers have not released an update to fix it, you don't have a chance to prove or disprove the catalysts ability to do its job, because as was said more times than I want to try and count, you'll still have to trust the PCM.

The next thing for the technician to check and rule out is exhaust leaks, and the performance of the O2 sensors. Exhaust leaks are pretty straight forward, they rarely play "Hide and Go Seek". Keep in mind, an O2 sensor that is marginal may pass the PCM's test of it, and then turn around and not be able to accurately report the exhaust content and trick the PCM into a false result. At the same time keep in mind for that to result in a false catalyst failure, it would have to occur two times in a row. That fact alone reduces the chances of that occurring, but does not eliminate the possibility.

The technician must verify good fuel control, and fuel trim. Exhaust leaks obviously have a potential impact on fuel trim, but so do certain input signals that the PCM relies on to recognize when its inside or outside of the designed testing window. Different manufacturers use different routines to establish their testing thresholds, GM typically tests at idle and they don't even have to of completed their O2 sensor monitors. If by chance one of the O2 monitors fail after the catalyst monitor has run, the decision could be made by the PCM to suspend the result depending on the results of the next test. Ford on the other hand runs the O2 sensor monitors, and then completes the catalyst testing under varying light load conditions. If the O2 sensor monitors do not complete, it should be expected that the Ford system will not even attempt to run the catalyst monitor. BTW, do leave room for exceptions as neither of these are hard facts, just tendencies. Always refer to service information for specific details on any vehicle you need to diagnose.

One of the biggest issues with P0420, and P0430 codes has to do with investigating why the catalyst failed in the first place. We can argue this one till the end of time but it's my opinion that far more catalysts are killed by external causes than simply die of old age. Sure both types of catalyst death occur and I have no statistics to prove my assertion that converters are more commonly killed than get to live to old age. But in a limited study of two vehicles to support my take on the matter I do have data that I collected from have two rather common vehicles, a 1999 F150 with 287K miles, and a 2002 Ford Explorer with 143K that both have all of their original catalysts on them and all of them are still going strong.

[1999 Ford F-150, Emissions Scan Data]

[2002 Ford Explorer XLT, Emissions Scan Data]

Now when you look at those captures for the catalyst you see the pids called rear to front switch ratio. Things like that, and descriptions from many manufacturers about how they compare the O2 sensors outputs during the onboard testing of the catalysts is what I believe leads to the misconception that technicians in the field should be able to evaluate a catalyst by watching the sensors. Let's see if we can explain why it just won't work for us, and it's not about what we can see which are the O2 sensor signals, its all about what we can't see and that is exactly how efficient the catalyst should be right at the time the technician is looking at the data.

There are a lot of things to consider about a catalyst and how efficient it should be. Of course the age of the assembly is important, and when it comes to replacement catalysts, construction and its size (the volume of and the percentage of the elements inside it) are critical. But for now, lets concentrate on just the O.E. version and what we can ascertain. When the engineers set up to test a catalysts efficiency and of course to decide when it is no longer capable of doing the job that it has been assigned they took on the task of trying to predict what the converter would do under a specific range of conditions. To do that they rely on a process called modeling. The short and not perfectly accurate explanation of modeling would be where they first had to predict if the vehicle was driven under specific conditions that the catalyst would be a specific temperature. Then with a given airflow (engine load), fuel trim, engine rpm, and the heck if I know what all else, the locus length of the upstream sensor would be XX times longer than that of the downstream one.

Locus length is pretty well defined by another member of the iATN as the length of a piece of a string that if you took a specific period of time and graphed out the O2 sensor, you could lay that string on top of the graph and measure its length. You would then repeat that for the down stream sensor and measure that string for the same period of time, and that ratio between them is the answer to how well the catalyst worked at that moment. As a technician, you could see sensor output that could easily be interpreted as the converter operating, but you could also see just the opposite result at any point in time. You have no way to know just how efficient the converter should be right now, if it is even lit off at all. Even worse, you could accidentally be looking at the sensors while the PCM is actually running the test, and its intentionally forcing the rear O2 sensor to move and it would easily look like a bad catalyst to you, when the PCM happens to be ready to pass it.

If you had a way to know exactly what the sensors outputs should be at a given catalyst temperature, and engine load, and every other variable that the engineers decided was pertinent, then and only then could you try and make sense from the sensor outputs. But even that would be only for that one specific moment in time, and not necessarily through the catalysts entire expected range of operation. By modeling the engineers work to predict what the catalyst will do under a wide range of conditions and one that (just) passes under one specific set of circumstances may fail under others.

So what does all of this mean? When you retrieve a P0420/P0430, inspect for the things that you have the ability to check, and in their absence there is nothing else you can do but trust the PCM, and make sure to the best of your ability that there are no conditions with the vehicle that are likely to kill the new one.

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