Sherlock Holmes DiagnosisNACAT

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”

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

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

“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.

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?

Sherlock Asks

• Concern just Start?

• Last Week?

• Last Month?

• What happened or what repairs were done right before the problem started?

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 StudyChrysler 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