Sherlock Holmes Diagnosis NACAT July, 2010 Jim Morton Jim Halderman

Introductions Jim Morton-(aka Sherlock Holmes) Jim Halderman-(aka Mr. Watson)

Topics to be Discussed Teaching the diagnostic process Interviewing the customer Interviewing the vehicle Interviewing the vehicle history The repeatable diagnostic procedure Tips and tricks

Teach Diagnosis? Do you teach a diagnosis procedure? If so, in which course? All of them? We both teach diagnosis in all courses It helps make the subject “real world” 4

Here is What We Hear We get asked for help after they have tried EVERYTHING What we usually find is that they had no real direction or approach Is this happening to you too?

Isn’t this what is important? We all teach how to perform tests such as a compression test Is a compression test the first test that should be performed for a driveability problem? Not so much how to test, but a TRUE game plan on each driveability concern

General Tests Decide what GENERAL test would eliminate some of the possible causes In most cases we have the problem nailed after 3 general tests to the right circuit or component

Pinpoint tests We then decide what Pinpoint test to perform to find the root cause

The Old Days My father opened the hood and felt the movement or play in the cooling fan Sir, you need a water pump 9

How Does it Work Today? We have to go through a diagnostic procedure to determine the root cause of the concern Then isolate the circuit or part and perform a pinpoint test to determine the root cause It is easy Mr. Watson if you ask the right questions 10

“The” Plan 8 steps Easy to remember Repeated the same way each time Has to be continuously repeated to students otherwise they tend to forget it

Like Peeling an Onion Get to the heart (root cause) of the problem requires some peeling and a plan of action

Finding the “ROOT CAUSE” In my mobile diagnostic business, a VERY normal statement is made to me “The SAME component keeps failing” An example of this would be 3 electric fuel pumps in 2 years replaced on the same vehicle

First Step Verify the concern (sounds better than complaint?) If the concern can not be verified then the repair can not be verified either Interview the owner (driver)

The Diagnostic Interview Also called the Sherlock Holmes Interview Interview the customer

Tech Tip Make sure you are talking to the person that noticed the problem/concern or the person that drives the vehicle the most ! NOT the person that happens to be the most convenient to drop the vehicle off Remember YOUR time is valuable also. 17

Is there a Problem? Describe the problem/concern Is there actual a problem? Does the customer know how to work all of the accessories etc.? Does the technician know? 18

Sherlock Asks Concern just Start? Last Week? Last Month? What happened or what repairs were done right before the problem started? 19

Interview the Vehicle

“The Milkman” My techs called me the “Milkman” They always saw me with my metal tray with a handle carrying handheld diagnostic tools

“The Milkman” What the “Milkman” was doing was going from vehicle to vehicle with the diagnostic interview sheet and performing basic “G” (General) tests

“The Milkman” Results of my “visual inspection” and “G” tests would indicate what circuits or components I felt needed “P” (pinpoint) testing

TEST DRIVE THE VEHICLE

Milk the DTCs A VERY good thing to look for when a DTC stores is the FREEZE FRAME look at what the fuel trim is, especially when there is a P0420 catalyst efficiency code Was the PCM trying to make a correction for fuel delivery?

Milk the DTCs P0420 Worksheet 1. Check for TSBs and calibration updates 2. Check exhaust condition (leaks) 3. Verify fuel control 4. Replace the catalytic converter 5. Verify the repair

ST & LT Fuel Trim

Fuel Trim Control The fuel trim value is a very important diagnostic tool, if the fuel trim is very positive, like +23%, why did the PCM have to add some much extra fuel to it’s base calculation ?

“The Bends and Ends”

Checking TSBs FORD: 2005-2006 Crown Victoria LINCOLN: 2005-2006 Town Car This article supersedes TSB 06-02-8 to update the Service Procedure. ISSUE: Some 2005-2006 Crown Victoria police and taxi vehicles built before December 13, 2005, and 2005-2006 Lincoln Town Car Limo vehicles may exhibit a malfunction indicator lamp (MIL) on with diagnostic trouble code (DTC) P0305, possibly accompanied with P0316, P0171, and/or P0174, especially after extended idle. This condition may be caused by fuel vaporization near injector Number 5.

Fuel Cut-Off Mode

Comparing PIDs A bad redundant ground circuit causing the TP and MAF to go haywire

Comparing PIDs Take notice of unstable idle due to ignition timing changing

High Authority Inputs The engine RPM signal comes from the CPK sensor and it must be able to calculate the engine speed very quickly As the number goes up, the engine is going faster This is usually the most important input

High Authority Inputs This signal is used as the basis for the fuel injector pulse signal.

MAP Relationship

Take Note that frame #9 there is only 1.7 “hg of manifold vacuum In frame # 17 there is 10.2 “hg of manifold vacuum

Narrow the problem to a system or cylinder This is where the “G” and “P” testing comes in Use a “G” (general) test to isolate the problem to a system or cylinder (or bank) Then use a “P” (pinpoint) test to drive down that FUNNEL in order to find the problem.

Ford Motor Co

Finding the ROOT CAUSE As stated in Jim Halderman’s Advance Engine Performance book Always ask the “5 WHYS” When you find the customer’s complaint, ask WHY 5 times

Finding the ROOT CAUSE Example of this would be a P0420 code (low catalyst efficiency) 1 why – because the pre & post oxygen sensors reading incorrectly 2 why – because air fuel ratio is too lean 3 why – because the fuel delivery is inadequate 4 why – because the fuel pump pick-up is partial clogged 5 why – dirt in fuel tank

Verify the Repair & Clear DTCs This is an important step for 2 reasons: 1 – YOU want to be the one to find that the repair didn’t work, not the customer. 2 – The are a lot of times that another DTC will not be set because there is a program that won’t allow a circuit to be monitored due to the current DTC. This is known as a “SUSPEND” condition

Case Study Chrysler mini van no-start Customer stated that it would not start unless he pounded on the dash. Finally, the vehicle wouldn’t start at all. Step #1-Verify Engine did not start No spark No Squirt

Step#2- Visual Inspection Yep the customer pounded on the dash So hard that the needles fell off

Step #3 Check DTCs

Step #4 Checked for TSBs-nothing that was related Checked archives of www.iatn.net Bingo- found several fixes for wiring being burned near the CPK sensor

Step #5 Scan Data No engine RPM while cranking

Step #6- Narrow Down

Step # 6-Continued

Step #7 Root Cause

Step #8-Verify Repair

Final Thoughts How does the PCM put all this information together and run the engine? You have to think like a PCM

Summary We are recommending that you teach a diagnostic procedure in all courses Repeat, repeat and repeat the process over and over This way students will know what and why they are doing what test

Contact Information Jim Morton matsauto@verizon.net Jim Halderman jim@jameshalderman.com