Cummins fault code 1977 is documented on this DiagTechPro library page for Cummins ISM CM871 (2007-09) engines, where it flags a Aftertreatment Fuel Injector 1 Circuit – Current Below Normal, Or Open Circuit condition (SPN 3556, FMI 5/5, Amber lamp). This 7-page PDF reproduces the manufacturer description, shop talk, component location and step-by-step troubleshooting so technicians can confirm and clear the code.
Cummins fault code 1977 overview
Cummins defines this code as “AFTERTREATMENT FUEL INJECTOR 1 CIRCUIT – CURRENT BELOW NORMAL, OR OPEN CIRCUIT” on the Aftertreatment Fuel Injector. The aftertreatment fuel injector is used to inject fuel into the exhaust system. Diesel fuel is sprayed into the exhaust system when the aftertreatment diesel particulate filter needs to be regenerated. The hydrocarbons in the diesel fuel are converted into heat in the aftertreatment diesel oxidation catalyst. The heat produced by the aftertreatment catalyst is then used to actively regenerate the aftertreatment diesel particulate filter, converting trapped soot into ash. The aftertreatment fuel injector is electronically controlled by the engine electronic control module (ECM) through a pulse width modulated (PWM) signal. The amount of fuel injected is determined by how long the PWM signal to the injector is on.
The document’s shop talk section highlights the following:
- An open circuit in the supply or return wire in the engine harness.
- An open circuit in the aftertreatment fuel injector solenoid.
Official document details
| Brand | Cummins |
| Model coverage | Cummins ISM CM871 (2007-09); Cummins ISX CM871 (2007-09) |
| System / Group | Aftertreatment Fuel Injector — ISM CM871 fault codes |
| Fault code | 1977 (SPN 3556, FMI 5/5) |
| Source | TruckFaultCodes.com Cummins fault code reference (© 2017) |
| Pages | 7 |
| File size | 0.5 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification (PID, SPN, FMI, lamp)
- Description
- Shop Talk
- Component Location
- Troubleshooting Steps
Applicable truck models and engines
This document applies to Cummins ISM CM871 (2007-09); Cummins ISX CM871 (2007-09) equipped diesel engines that log Fault Code 1977 on the Aftertreatment Fuel Injector. Always confirm engine calibration and use a Cummins diagnostic tool such as INSITE to read live data before starting repairs. Full engine specifications and service information are published on the Cummins official website.
Who needs this Cummins fault code 1977 manual
Heavy-duty truck technicians, fleet workshops and owner-operators diagnosing an electronic control module warning on ISM CM871 engines will use this sheet to verify SPN 3556 before parts are replaced.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download.
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