Table of Contents 652 Body Electrical Diagnosis Finding Possible Problem Areas ........................................................ 171 Where to Begin ............................................................................... 171 The Split-Half Method ..................................................................... 172 Step #5 – Correct the Trouble ............................................................ 173 Component Service Hints ............................................................... 173 Step #6 – Check for Proper Operation ............................................... 174 Section 5:
Diagnosing Body Electrical Topics ................................................................................................. 177 Introduction ......................................................................................... 178 Diagnosing Open Circuit Problems .................................................... 178 Problems Using a Voltmeter on Open Circuit Problems ................................. 179 High Resistance Problems ................................................................. 186 Causes of a High Resistance Problem ........................................... 186 Diagnosing High Resistance Problems ..........................................
187 Determine if There is Current Flow in the Circuit ........................ 187 Isolating a High Resistance Problem .............................................. 188 Parasitic Load ..................................................................................... 196 How to Measure Parasitic Load ...................................................... 197 Diagnosing Parasitic Load .............................................................. 198 Disconnecting Components ................................................................ 199 Procedure for Mapping Current Flow Through the J/Bs .................
200 Diagnosing Shorts to Grounds ........................................................... 201 Inspect the Fuse ............................................................................. 201 Short to Ground Diagnostic Strategy .............................................. 201 Selecting a Load ............................................................................. 202 Using a Headlamp as a Load ......................................................... 202 Intermittent or Continuous? ............................................................ 203 Disconnecting Component Connectors ..........................................
203 Feedback Problems ............................................................................ 211 Diagnosing a Feedback Problem ................................................... 211 Quick Checks for Lighting Circuits .................................................. 212 Quick Checks for General Feedback Problems ............................. 212 If the Quick Checks Do Not Find the Cause ................................... 213 The 6-Step Diagnostic Process ...................................................... 214 Section 6: Diagnosing with Topics .................................................................................................
217 Diagnosing with Techstream .............................................................. 218 Techstream Electrical or Electronic .................................................................... 218 Electronic Control Units (ECUs) .................................................... 219 Logic Function ................................................................................ 219 How ECUs Work ............................................................................. 220 Diagnosing Electronically Controlled Circuits ................................. 221 Verifying Inputs Using Data List .....................................................
222 Verifying Outputs Using Active Tests ............................................. 223 Follow-up Diagnosis ....................................................................... 224 Technical Training v