DerateMack Diesel ECM

U029D-00

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

Engine protection and emissions inducement power-limiting faults.

Call Now Request a Quote Create Service Ticket

Active derate — truck is losing power now

System

Mack Derate

Mack ECM Service

Diagnostic Overview

Mack fault code U029D-00 usually indicates lost communication with a NOx sensor module. If the ECM cannot communicate with a NOx sensor, the SCR system cannot accurately confirm emissions performance and may enter warning or derate logic. This is often an electrical, power, ground, or CAN communication issue.

Likely Causes

Failed NOx sensor module; power or ground loss; data-link wiring issue; connector corrosion; damaged harness; low system voltage.

What To Check First

Check NOx sensor power, ground, connector condition, and CAN communication before replacing the sensor.

⏵ Truck down? Fleet stalled?

Active Derate? Get Help Right Now.

Send us your fault codes and operational context. Same-day quote, remote diagnostic available, ship-in service nationwide.

Create Service Ticket

Internal Linking

Related Derate Fault Codes

View All Derate Codes

P0087-00

Mack fault code P0087-00 indicates low fuel rail or fuel system pressure.

P009B-13

Mack fault code P009B13 generally relates to the fuel pressure relief control circuit or fuel pressure control system.

P103C

Mack fault code P103C is commonly associated with SCR/NOx conversion testing or aftertreatment performance on Mack/Volvo platforms.

P1130-00

Mack fault code P113000 is generally an emissions or sensor-performance fault that can contribute to derate depending on engine calibration.

P203A-13

Mack fault code P203A13 generally points to a DEF/reductant level sensor circuit issue.

P203C-00

Mack fault code P203C00 commonly indicates a low signal or circuit problem from the DEF/reductant level sensor.

View All Derate Codes →