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Fast diagnostic approaches

In the first of two problems, techincians learn a quicker way to diagnoses.
Tuesday, June 5, 2012 - 11:02
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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.

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