Cummins CM850 ISB ISC ISL QSB QSC QSL Engine Control System Troubleshooting & Repair Manual Volume 2 (Bulletin 4021416) – PDF Download

Description

Cummins CM850 Electronic Control System Troubleshooting and Repair Manual Volume 2 takes the technician straight into fault-code diagnostics for the CM850 control platform used across the ISB, QSB, ISC, QSC, ISL and QSL engine families. Volume 2 is the fault-code reference: the codes running from 351 through 1668 are each handled as a self-contained troubleshooting tree, with the circuit description, component location, shop talk notes and step-by-step test procedure needed to isolate the fault and confirm the repair. It is the volume you keep open when INSITE is connected and you need to know which pin to probe next.

File Details

• Manual type: Troubleshooting and Repair Manual, Volume 2
• Brand / publisher: Cummins Inc.
• Electronic control system: CM850
• Engine families: ISB, ISBe2, ISBe3, ISBe4, QSB4.5, QSB5.9, QSB6.7, ISC, QSC8.3, ISL, ISLe3, ISLe4, QSL9
• Language: English
• Page count: 810 pages
• File format: PDF
• Document number: Bulletin 4021416
• Publication date: 01-April-2014

Chapters Covered

The volume is built around two main sections plus an index, and the fault-code work itself is grouped below by system for easier navigation.

• Introduction (Section i)
• Troubleshooting Fault Codes (Section TF)
• Index

Introduction and Safety Information

Section i sets the ground rules for working on a CM850-controlled engine: general safety instructions, the warning and caution symbol set used throughout the manual, welding precautions for vehicles with electronic fuel systems, general repair and cleaning guidance, acronyms and abbreviations. It is short compared with the fault-code chapters, but it establishes the conventions that the troubleshooting trees in Section TF rely on.

Sensor Supply, Accelerator Pedal, and Idle Validation Circuits

This group covers the +5 VDC sensor supply and the throttle-side circuits that feed it: faults 352 and 386 for supply voltage below or above normal, 387 and 443 for the accelerator pedal supply, and the idle validation codes 431 (ISS, NISS and SSS variants), 432 and 551 (ISS, NISS and SSS variants). The pedal position sensor codes 1239, 1241 and 1242 are also here. Each tree walks the harness pin-by-pin between sensor, OEM harness and ECM, with resistance and voltage specifications listed in the step tables.

Data Link, ECM Power Supply, and Communication Faults

SAE J1587/J1922 and SAE J1939 communication problems are handled in their own trees: fault 412 (J1587/J1922 cannot transmit), 426 (J1939 cannot transmit) and 427 (J1939 abnormal update rate). The power-side codes 434, 757 and 1117 cover unswitched battery supply loss, ECM data loss and power loss without ignition off, including the injector harness and rocker lever chafe checks that can set 1117. Komnet datalink fault 1633 is also included for OEM networks.

Fuel Rail Pressure, Injector Circuit, and Water-in-Fuel Faults

The fuel system trees are the technical core of this volume. Rail pressure codes 449, 451, 452, 553, 554 and 559 are worked through with sensor checks, lift pump and gear pump pressures, drain line restriction tests and relief valve leak-down procedures. The water-in-fuel sensor codes 418, 428 and 429 cover the drain, resistance and short-to-ground checks. Injector power supply fault 351 sits here as well, with the pass-through connector and engine harness pin-out.

Lubrication, Battery, and Charging System Faults

Oil pressure and oil level codes 415, 435, 471, 498, 499 and 688 are grouped here, along with the battery and charging codes 441, 442, 596, 597 and 598. The trees include mechanical oil pressure gauge checks, sensor resistance and PWM signal tests, charging rate checks and the unswitched battery supply and fuse inspections that back up the ECM power codes.

Turbocharger, EGR, and VGT Faults

Turbocharger speed and boost codes 545, 595 and 687 sit alongside the compressor inlet temperature codes 691 and 692 and the EGR/VGT position codes 957, 958, 1228 and 1229. The trees cover wastegate actuator inspection, VGT position sensor response tests, sensor supply and return checks, and air gap and tone wheel inspection where the turbo speed signal is suspect.

Engine Speed and Position Sensor Faults

Crankshaft and camshaft sensor diagnostics are handled in codes 689, 731 and 778. The trees step through supply voltage, sensor state changes, air gap checks and tone wheel inspection, and 731 adds the static timing and engine grounding checks that apply when the cam and crank signals are out of phase.

Aftertreatment, Catalyst, and Exhaust Temperature Faults

Catalyst-related codes 1663, 1664, 1665, 1666, 1667 and 1668 cover swapped inlet/outlet sensors, missing catalyst, exhaust gas temperature circuit faults and catalyst tank level sensor faults. The trees include sensor resistance tables, pin-to-pin and pin-to-ground shorts, catalyst presence and soak-time checks.

Misfire, Cylinder Imbalance, and Injector Driver Faults

Cylinder power imbalance fault 951 and the individual misfire codes 1654 through 1659 use the INSITE cylinder cutout and automated cylinder balance tests, with guidance on valve lash, engine brake adjustment, injector swap testing and air compressor timing. The injector solenoid driver codes 1139 through 1145 cover unintended fueling per cylinder, with the blocking tool procedure for isolating a stuck-open injector.

Starter Relay, OEM Switch Inputs, and Maintenance Monitor

The starter lockout relay codes 584 and 585, the OEM switch inputs 497, 523, 528, 779 and 1639, the auxiliary outputs 527, 529 and 599, and the oil change reminder 649 are collected here. These trees are aimed at OEM-installed hardware, so they lean on the OEM harness pin-outs and the switch or solenoid resistance checks that confirm the fault is in the vehicle side rather than the engine.

Built for Real CM850 Fault-Code Work

This is not a general engine overhaul book. Volume 2 is the fault-code companion to the CM850 system, and it is structured so that a technician with INSITE connected can move from active code to confirmed repair without guessing. Each code begins with the reason, effect and lamp status, then walks through the diagnostic steps in the order Cummins recommends, with the specification or repair value listed next to the action. Where a fault can be caused by more than one system — a rail pressure code triggered by a drain line restriction, for example — the tree calls out the cross-checks and the related codes that need to be cleared first.

The circuit diagrams that accompany many of the trees are the other half of the value. Injector circuit routing, sensor supply splits, data link topology and OEM harness connectors are drawn so that the pin numbers in the step tables match what is actually on the engine. Component location notes and shop talk entries fill in the practical detail — the connector that is easy to miss, the air gap that has to be measured hot, the fuse that feeds the ECM but is not in the engine harness. For a shop running ISB, QSB, ISC, QSC, ISL or QSL engines on the CM850 platform, this is the volume that turns a fault code into a test plan.

The tables inside each tree follow the same logic: a condition, an action, a specification or repair, and the next step. That format keeps the diagnostic path linear and makes it easy to hand a specific code to a second technician without losing the thread. Codes that commonly appear together — sensor supply faults with multiple sensor faults, or rail pressure codes with lift pump or drain line faults — are noted so that the first code cleared does not mask the second.

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Instant PDF Delivery

The Cummins CM850 Troubleshooting and Repair Manual Volume 2 is delivered as an instant PDF download — no shipping, no waiting for a disc. Open it on a laptop, tablet or phone in the bay, print the specific fault-code tree you need for the job, and keep the rest of the 810-page manual on file for the next code. Every page in this PDF is the CM850 Volume 2 content published under Bulletin 4021416, April 2014.