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Duramax LML & LGH Diesel

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Case Study

Duramax engines are not designed and produced by the manufacturer that sells them. This means that the people who created the engine management and emissions systems and the people who wrote the repair information didn't always understand each other. Repair information is becoming scarce and inconsistent for all vehicles, but is even worse for these Bosch fuel systems, Isuzu-designed engines, and GM vehicles.

This manual and class were designed specifically to give technicians a clear diagnostic path.

ATG spent months collecting and comparing technical information to fill in the holes of the repair information, and then diagnosed and repaired these engine management and emissions systems to validate everything we found.

This 200-page manual is the only place you'll find explanations that not only tell you which tests to run in what order and what the test results should be, but why, and what your options are when a test fails.

Table of Contents Page
LML & LGH Duramax  
Duramax Evolution  
Generations 8
Overview 8
Things You Need to Know  
Warnings 11
GM Bulletins 12
LML & LGH Differences 12
Crankcase Ventilation 12
Head Gasket Selection 14
Dual Thermostats 15
Warrantying Your Engine Work? 16
Identifying Power Up Software 17
Aftermarket ‘Foolers’ 22
Alternative Power Up Identification Strategies 22
TCM Peak Torque – The Secret Power Up Clue  23
Air Intake System  
Basic Intake System  
Overview 25
Mass Airflow (MAF) Sensor 26
Manifold Absolute Pressure (MAP)/Boost Pressure Sensor 27
Intake Pressure PID Example 28
Intake Air Heater (IAH) 29
IAH Scan Tool Control 31
Intake Air Temperature (IAT) Sensor 31
Intake Air (IA) Valve  31
Intermittent High Idle Bulletin 31
Turbocharger Overview 32
Variable Vane Turbo (VVT), Variable Geometry Turbo (VGT) 32
Closed Loop:  Vane Position Solenoid & Vane Position Sensor 34
Vane Position Sensor Replacement 35
Vane Position Solenoid Circuits & Activity  35
Closed Loop Boost Control Scan Tool Test 36
Normal Vane Position Solenoid & Sensor Relationships 38
Learned Vane Position  39
Scan Tool Vane Learning 41
P003A – Vane Position Not Learned 41
Other Turbo Controls – Vane Position Solenoid  43
Other Turbo Controls – Vane Position Sensor 43
OEM Scan Tool Turbo Control Variations 44
Turbocharger Coolant Bypass 45
Common Turbocharger Smoking Faults 45
Turbocharger & Intake Noises  46
Turbocharger Mechanical Damage 47
Intake Leak Diagnosis (ALER & ISLI PIDs) 48
Exhaust Brake 51
Glow Plug System  
Glow Plugs  
Overview 52
Glow Plug Control Module (GPCM) 52
Glow Plug Faults 53
Glow Plug Service 54
Glow Plug Fault Codes 54
Glow Plug PIDs – PCM  55
Glow Plug PIDs – GPCM  55
Scan Tool Glow Plug Controls 58
Glow Plug Lab Scope Test 59
Fuel Systems  
The Whole Enchilada  
Overview 61
Fuel Supply Suction System  
Supply Side Fuel Flow 63
Tank & Fuel Tank Module 64
Van Electric Priming Pump  64
Fuel Filter/Fuel Conditioning Module 65
Fuel Filter Vacuum Switch  67
Fuel Filter Warnings  67
Fuel Filter Replacement 68
Fuel Filter Life Reset  69
Manual Fuel Filter Life Reset  70
Aftermarket Fuel Filters 70
Low Pressure System Faults & Symptoms 71
Supply Side Vacuum Test for Restrictions 71
Fuel Aeration & Leak Test Overview 74
Primer Pump Pressure Test 75
High Pressure Pump Draw Test  77
Interpreting Primer Pump & High Pressure Pump Draw Test Results 78
Filler Neck Pressurization Test 78
Fuel Aeration – Finding Supply Side Leaks 79
Fuel Aeration Clear Line Test 79
Manual Supply Path Vacuum Test 81
Hey, I Can See the OEM Diagnostic Path From Here! 82
Intermittent Faults or a Worn Suction Pump? The Aftermrkt Pump Alternative 83
Fuel Conditioning Module Service 83
High Pressure Fuel System  
High Pressure Side Fuel Flow 84
Bosch CP4 High Pressure Pump 84
Pump Timing 85
High Pressure Pump Failures 86
Fuel Pressure Regulators (FPR1 & FPR2) 88
FPR1 & FPR2 PID Activity 89
Fuel Temperature Sensors 1 & 2 90
Fuel Lines 91
Fuel Rails 91
Fuel Rail Pressure (FRP) Sensor 92
Fuel Pressure PIDs  93
No-Start/Hard Start – Checking Cranking Fuel Pressure 94
Scan Tool Fuel Pressure Control 94
Scan Tool High Pressure Pump Peak Output Test  96
FPR2 & High Pressure Pump Output Test  97
Return Line Race Fuel Valves? 98
Direct Fuel Injectors 98
Lab Scope Fuel Injector Testing 100
Injector Hydro-Mechanical Operation 103
Injector Balance Rate PIDs 104
Balance Rate Polarity vs. Likely Faults 105
Misfire Codes vs. Balance Rate Codes 105
Misfire vs. Balance Rate PIDs 106
Scan Tool Fuel Injector/Power Balance Test 108
Scan Tool Injector Adaptive Value Reset  110
Pilot Injection Balance 111
Injector Quantity Adjustment (IQA) Programming 113
Injector Return Rate Testing 116
Injector Replacement 119
High Pressure System Fuel leaks 119
Pressurized Fuel Return System  
Constant Pressure Regulator 120
Fuel Return Connections 121
Backfill Valve 121
Constant Pressure Regulator Testing 122
Symptom Testing Strategies - ATG Symptom Tests  
Overview 124
GM’s Starting Point:  The Diagnostic System Check 125
GM’s Second Step:  Review Strategy Based Diagnostics 126
GM’s Third Step:  Preliminary Tests  126
How to Use ATG Symptom Tests  127
No-Start 127
Hard Start – Cold Only 128
Hard Start – Hot Only  128
2012 LML No-Start Case Study 129
Hard-Start or Start & Stall 133
Hesitation, Sag, Stumble 134
Misfire or Rough Idle 135
Multiple Misfiring Cylinders  136
Misfiring with White Smoke  137
Stalling 137
Surging 137
Poor Fuel Economy 138
Low Power 139
Black Smoke 140
White Smoke 141
Blue/Gray Smoke 142
Any Color Smoke – Only During Regeneration  142
Knocking/Pinging 142
Comprehensive Fuel System Test 143
Emissions Systems  
Exhaust Gas Recirculation (EGR)  
Overview 144
EGR Valve & Position Sensor  144
EGR Enabling & Operating Conditions 146
EGR Cooler Bypass Valve 147
EGR Cooler & Bypass Paths  148
EGR Temperature Sensors – EGT1 & EGT2 149
EGR, EGR Cooler, & Bypass Valve Faults 150
EGR System PIDs 152
Scan Tool EGR Valve Control 153
Scan Tool EGR Cooler Bypass Valve Control 154
EGR & Bypass Verification Trick Summary 155
Aftertreatment Systems Overview  
DOC, DPF, SCR, DEF – So Many Acronyms! 156
Exhaust Gas Temperature (EGT) Sensors 157
Diesel Oxidation Catalyst (DOC) & Diesel Particulate Filter (DPF)  
Overview 158
Diesel Oxidation Catalyst (DOC) 158
DOC Faults 158
DOC Quick Check 159
Diesel Particulate Filter (DPF) 159
DPF Faults 160
Closed Loop:  DPF Differential Pressure Sensor 161
Regeneration & DPF Service Life 161
Soot Accumulation Rates & Regeneration Frequency 162
Passive vs. Active Regeneration 162
Active vs. Service (Forced) Regeneration 162
Driver Information Center (DIC) Messages & the P2463 162
HCI: The 9th Injector 164
HCI Faults 165
The Post-Injection Backup Plan 166
HCI Diagnosis 166
HCI Service & Bleeding (DPF Regeneration Enable) 167
Exhaust Air Cooler (Diffuser) 168
Intake Air (IA) Valve 168
Intake Air (IA) Valve Scan Tool Control 169
Service Regeneration Conditions 169
Service Regeneration Termination Conditions 169
Service Regeneration – What to Expect 170
Warnings & Lawyer-Repellent 170
Service Regeneration Example 171
Regeneration Soot Reduction 173
Codes Set During Regeneration 174
Inhibited Regeneration  174
Scan Tool Regeneration Enable  174
Selective Catalyst Reduction (SCR) & Diesel Exhaust Fluid (DEF)  
Systems Overview 175
SCR Operation 175
Refilling the DEF (Reductant) Tank 176
Closed Loop Control – NOX Sensors 177
DEF Tank & Reductant Pump Module 179
Reductant Sensor Module 179
Reductant Level Sensor 180
Frozen DEF & DEF Heaters 181
Scan Tool DEF Heater PIDs & Controls 181
Key-Off Injector & Pump Purging 181
DEF Injector 182
DEF Diffuser 182
DEF Pump Testing 182
DEF Injector Testing 183
SCR/DEF DIC Warning Message Summary 183
SCR/DEF DIC Warning Sub-Messages Summary 185
DEF Level Warning Levels 185
Refill Detection 186
Forced Refill Detection 187
DEF Quality Warning Levels 188
Service DEF System:  Fault or Tampering Warning Levels 189
Post-Repair Procedures 191
Scan Tool SCR/DEF Resets 191
Reductant Fluid Quality Test (RFQT) Setup 192
Scan Tool RFQT Test Procedure 193
RFQT Critical PID Review 194
Scan Tool RFQT Test Examples 195
Messages Won’t Clear?  Your Therapist Says ‘Read This First’ 198
Suggested Order of Repair – TSB 12-06-04-002 199
DEF Warning Messages Won’t Clear – PIP 4864 199
‘Exhaust Fluid Quality Poor’ Message Won’t Clear – PIP 5007 200
‘Exhaust Fluid Quality Poor’ Message Won’t Clear – PI 1214 202
Permanent Codes & Code Buckets – TSB 12-06-04-002 203
Reference Information  
Wiring Examples  
Note About Examples 206
NOX Sensor Network – Powertrain Expansion Bus 206
Basic Sensors 207
High & Low Pressure Fuel Components 208
[High Pressure Fuel Injectors 209
\\EGT & DPF Sensors  210
EGR & Turbocharger Systems 211
APPS & Engine Position Sensors 212
Startability:  Glow Plugs & IAH  213
Aftertreatment:  SCR & DEF  214

Duramax Intake/Exhaust Leak Check Shortcut

The manual is over 200 pages long, the case study below is a quick sample to show how we leverage underused PIDs to save hours of testing.

This case study used an aftermarket scan tool example, it shows the air leak PID, which is a built-in leak indicator. The manual includes a table to interpret the values. If the EGR is commanded closed and the value is near '1.0', then you don't have to waste any time looking for a boosted or unboosted intake leak, and exhaust leak, or a poorly seating EGR valve. The PCM already did the work for you!

This simple example is one of dozens that show the fastest methods for eliminating the most possible causes with the least effort. It could be said that the point of the manual is to to take apart as little as possible during diagnosis. Even better, we've woven these tests into decision- making indicators so you don't miss anything.


Air Leak PID Graphing Example




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