AftertreatmentCaterpillar Diesel ECM

SPN 3360 / SPN 3820

Name: ECM Performance
Address: Fort Lauderdale, FL, 33325, US
Telephone: (888) 768-2447
Price range: $$-$$$

DPF, DEF, SCR, and NOx-reduction system faults.

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System

Caterpillar Aftertreatment

Caterpillar ECM Service

Diagnostic Overview

CAT codes listed as 3360/3820 generally point toward the DEF supply, DEF quality, DEF tank, or SCR dosing system depending on the exact FMI shown in Cat ET. These codes should be treated as aftertreatment support-system faults rather than a simple sensor-only problem. The ECM may be seeing a DEF system value that is missing, not plausible, or outside normal operating range. Because SCR performance depends on clean DEF, correct dosing pressure, and accurate sensor feedback, the full DEF system should be checked before replacing expensive components.

Likely Causes

Contaminated DEF; poor DEF concentration; DEF tank header fault; DEF pump issue; damaged DEF harness; crystallized DEF lines; poor connector contact; incorrect or missing FMI detail.

What To Check First

Retrieve the exact SPN/FMI in Cat ET, test DEF quality, inspect the DEF tank/header and harness, check DEF pump pressure, and look for related SCR or inducement codes.

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Related Aftertreatment Fault Codes

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SPN 1761 FMI 17

CAT fault code 1761-17 commonly relates to diesel exhaust fluid level or a DEF level signal that is below the expected range.

SPN 3361 / SPN 3821

CAT codes listed as 3361/3821 commonly belong to the DEF dosing or SCR control side of the aftertreatment system.

SPN 3474 FMI 31

CAT fault code 3474-31 is typically associated with aftertreatment regeneration or ARD-related operation.

SPN 3701 FMI 15

CAT fault code 3701-15 commonly indicates an aftertreatment condition that is above normal but at a least-severe level, often connected with DPF soot load, regeneration need, or aftertreatment restriction.

SPN 3701 FMI 16

CAT fault code 3701-16 usually represents a more serious aftertreatment condition than 3701-15, with the measured or calculated value above normal at a moderate severity level.

SPN 3719 FMI 0

CAT fault code 3719-0 is generally an aftertreatment soot-load or DPF restriction code at a high-severity level.

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