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Service Procedure Default Strategy

A referral strategy has been established to assist the technician with additional information when the cause of the failure cannot be determined. If no problem is found after performing diagnostics, then refer to the default matrix table for further diagnostic information.

DEFAULT MATRIX

Strategy Based Diagnostic Charts Initial Diagnosis Default Section(s)
On-Board Diagnostic (OBD-II) System Check Vehicle does not enter diagnostics. Chassis Electrical
On-Board Diagnostic (OBD-II) System Check Vehicle enters diagnostics and communicates with the Tech 2. MIL is "ON" in diagnostics. Engine does not start and run. Ignition System Check
On-Board Diagnostic (OBD-II) System Check Engine starts and runs, no ECM codes set. Customer complains of vibration. -
On-Board Diagnostic (OBD-II) System Check Engine starts and runs, no ECM codes set. Customer complains of harsh or soft shift, poor performance, delayed or no engagement into drive or reverse, transmission fluid leak, transmission noise or vibration, or improper TCC operation. Automatic Transmission
ECM Power and Ground Check On-Board Diagnostic (OBD-II) System Check. Chassis Electrical
ECM Power and Ground Check On-Board Diagnostic (OBD-II) System Check. ECM power and ground circuits OK. Data link voltage incorrect. Chassis Electrical
On-Board Diagnostic (OBD-II) System Check Engine starts and runs, no ECM codes set. Customer complains of harsh or soft shift, poor performance, delayed or no engagement into drive or reverse, transmission fluid leak, transmission noise or vibration, or improper TCC operation. Automatic Transmission
Symptoms Initial Diagnosis Default Section(s)
Intermittents
  1. On-board Diagnostic (OBD-II) system check.
  2. Careful visual/physical inspections.
 Chassis Electrical
Hard Starts
  1. OBD-II system check.
  2. ETC system check.
  3. Sensors (ECT, MAF, TP).
  4. Fuel system electrical test, fuel system diagnosis. (High, Low)
  5. Ignition system.
 Engine Mechanical, Ignition System Check, Exhaust System Diagnosis
Surges and/or Chuggles
  1. OBD-II system check.
  2. ETC system check.
  3. Heated oxygen sensors.
  4. Fuel system diagnosis. (High, Low)
  5. Ignition system.
 Calibration ID/Service Bulletins, Ignition System Check, Generator Output, Exhaust System Diagnosis, AW30-40LS System Test
Sluggish or Spongy
  1. OBD-II system check.
  2. ETC system check.
  3. Fuel system diagnosis. (High, Low)
  4. Ignition system.
 Exhaust System in Engine Exhaust, TCC Operation, Calibration ID/Service Bulletins
Detonation/Spark Knock
  1. OBD-II system check.
  2. Transmission range switch.
  3. TCC operation.
  4. Fuel system diagnosis. (High, Low)
  5. Ignition system.
 TCC operation, Cooling System, Ignition System Check, Calibration ID/Service Bulletins
Rough, Unstable, or Incorrect Idle, Stalling
  1. OBD-II system check.
  2. ETC system check.
  3. Fuel injector and fuel injector balance test.
  4. EVAP emission canister purge valve check.
  5. Ignition system.
 Throttle Linkage, A/C Clutch Control Circuit Diagnosis, Crankcase Ventilation System, Calibration ID/Service Bulletins, Generator Output Voltage (Chassis Electrical), Exhaust Diagnosis
Poor Fuel Economy
  1. OBD-II system check.
  2. Careful visual/physical inspection.
  3. Ignition system.
  4. Cooling system.
 TCC Operation, Exhaust System (Engine Exhaust)
Hesitation, Sag, Stumble
  1. OBD-II system check.
  2. ETC system check.
  3. TP.
  4. Fuel system diagnosis. (High, Low)
  5. Fuel injector and fuel injector balance test.
  6. EVAP emission canister purge valve.
  7. Ignition system.
 Generator Output Voltage (Chassis Electrical), Calibration ID/Service Bulletins, Ignition System Check
Cuts Out, Misses
  1. OBD-II system check.
  2. Cylinder balance test.
  3. ETC system check.
 Ignition System Check
Engine Cranks But Will Not Run
  1. OBD-II system check.
 Fuel System Electrical Diagnosis, Fuel System Diagnosis, Fuel Injector and Fuel Injector Balance Test.
Dieseling, Run-On
  1. OBD-II system check.
  2. Careful visual/physical inspection.
  3. Fuel system diagnosis. (High, Low)
 -
Backfire
  1. OBD-II system check.
  2. Ignition system.
  3. Fuel system diagnosis. (High, Low)
  4. Fuel injector and fuel injector balance test.
 Exhaust System Diagnosis, Intake Casting Flash, Ignition System Check
Misfire
  1. OBD-II system check.
  2. Ignition system.
  3. Fuel system diagnosis. (High, Low)
  4. Fuel injector and fuel injector balance test.
 Vibrations, Transmission, Driveshaft and Axle
Catalyst Monitor
  1. OBD-II system check.
  2. Careful visual/physical inspection.
  3. Heated oxygen sensors.
 Exhaust System
Fuel Trim
  1. OBD-II system check.
  2. Careful visual/physical inspection.
  3. Fuel system diagnosis. (High, Low)
  4. Heated oxygen sensors, MAF sensors.
 Exhaust System Intake Air System
Evaporative Emissions
  1. OBD-II system check.
  2. Careful visual/physical inspection.
  3. Fuel system diagnosis. (High, Low)
 -
Heated Oxygen Sensors
  1. OBD-II system check.
  2. Careful visual/physical inspection.
 Exhaust System
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