Fast diagnostic approaches

This month, a couple of TST members take on problems from other shops and share their experiences with us. let's look at the issues with a 2002 Ford and a 2005 Subaru.

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Quick Ford EGR Diagnosis
Contributed by TST Associate Ed Hazzard

I was called to a shop that had a 2002 Ford Expedition with a 4.6L engine. The shop owner said that the check engine light was on and the truck ran fine. The light needed to be repaired so the vehicle would pass the state inspection test.

I hooked up my Modis to the data link connector (DLC) to retrieve the diagnostic trouble code. A code of P0402 was stored in the truck’s PCM memory. A P0402 is an Exhaust Gas Circulation (EGR) excessive flow code. These are typical on Fords.

Then I looked at the DPFE data PID. My reading was 1.68 volts key on engine off (Figure 1). Is this a good spec or not (Figure 2)? According to Snap On Troubleshooter, it was just out a little bit, so my next step was to go and test it. I backed out of the troubleshooter and went into the component test section. Then I hooked up to the component as directed by my scanner and compared the reading on my meter to what the truck’s PCM is seeing. (See Figure 3.)

This is how I did it: I hooked up my Modis to the DPFE connector as a meter and tested the voltage at the connector itself. The voltage test was exactly like the scan data, so I replaced the sensor because it did not meet the specification. I was able to check for a code, scan the data, check the spec, test and verify the component all in 10 minutes.

Now I have time to get a cup off coffee and head to my next job.

Time to consider replacing CV axle boots?
Contributed by TST member Alex Portillo

Standard practice in the industry is to replace CV axles with torn boots with brand new CV axles made in China or rebuilt CV axles. The reasons behind it is that “new” axles are cheap and that replacement boots “don’t last.”

However, we ran into a couple situations where boot replacement was either (a) the only possible repair or (b) would have saved the customer a lot of money and the shop a lot of headache.

The first case involves a 2005 Subaru Outback where the vehicle had a shaking complaint. Another repair shop replaced the front left CV axle and the customer was sure that something else was wrong with the vehicle.

The customer was right, because the front driveshaft did have U-Joint play. Because the U-Joint is not a serviceable item on this vehicle the entire $640 driveeshaft had to be replaced. After the driveshaft was replaced, the vehicle still had a shake.

Lo and behold, we removed the rebuilt CV axle and it had major play. It was undetectable when installed in the vehicle and a new CV repaired this vehicle. As you can see in the picture (Figure 4), there were obvious internal defects in the axle sold as rebuilt. The customer would have saved himself a lot of money if he only had a boot replaced.

What does my shop use to replace CV boots? Personally, I use Flex Boots and an Astoria 2000 Flexx Boot installer. Three different part numbers cover about 95 percent of the CV axles out there, the boots fit snug, they last for years, and I can stretch the boot over the axle joint so I do not have to take it apart.

However, on 2008 Jeep Compasses there is a national backorder on dealer CV axles, and no aftermarket ones exist either. You cannot use a flex boot on these because the boots only fit circular CV axles. The repair for a torn boot? A brand new CV boot with little bumps in it from the dealer (Figure 5).

I know a lot of shops still refuse to service CV boots, but I’m not sure if that old wisdom should still apply today. We are taking a lot of liability when we do a repair and sometimes boot replacement is the only way you can make money and ensure there is no comeback.

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