Genuine Mack Engine Control Module
| DESCRIPTION | Engine Control Module |
| CONDITION | Used |
| BRAND | Mack |
| PART NUMBER | 21358126 |
| PART NUMBERS | 21358126; 85020757, 20583789, 20977021, 21042371, 21107008, 21300060, 85003744, 85013244, 85021349, 85003745, 701003AT |
Function of this part
The engine control module (ECM) is the electronic brain of the engine. It reads information from sensors and commands fuel delivery, timing, and other actuators to keep the engine running properly.
Why this part matters
Without a functioning ECM, the engine will not start or will run poorly. A correct, working ECM is essential for performance, diagnostics, emissions control, and protecting the engine from damage.
About the brand
Mack is known for building tough trucks and components for construction, vocational, and highway fleets that need reliable performance day after day.
Fitment & usage
Used OEM parts are a smart choice for controlling repair costs while still using original-equipment components. Always match the OEM part number(s) listed to your existing part, and consult your service manual, dealer, or technician if you are unsure about fitment.
Note: Because this is a used component, normal signs of wear such as scratches, discoloration, or light surface corrosion may be present. Refer to the product photos and information on Second Truck Parts for the best representation of the part you will receive.
General Shipping
Our estimated shipping times are based on transit times and do not include processing or manufacturing. Processing times typically range from 24 to 48 hours. For precise processing and shipping times, contact our customer service. Address updates post-shipping must be coordinated with our customer service, and any associated charges will be the customer's responsibility.
Shipping Methods & Transit Times
- Small Package Saver: 3 to 7 business days*
(For products under 10 pounds and most items eligible for FREE SHIPPING) - Ground: 1 to 6 business days*
(Most packages are shipped via UPS, occasional use of FedEx) - Second Day Air: 2 to 3 business days*
(Contact our sales department) - Next Day Air: 1 to 2 business days*
(Contact our sales department) - Canada: 1-6 business days*
(Transit times may vary due to border customs) - Large Package Rate: 3-5 business days*
(For residential deliveries) - Will Call: Customer Pick Up
(Available upon request, no shipping or handling charges)
*We process and ship orders Monday through Saturday, excluding major U.S. holidays. Most orders ship from our North Carolina warehouse.
Freight/Oversize Shipments
Freight/LTL shipping applies to commercially zoned properties only. Non-commercial addresses may incur additional shipping charges. When receiving a freight shipment, carefully inspect and note any exceptions or damages on the receipt. Additional services like lift gates may carry extra fees charged by the freight carrier, at the customer's discretion.
Free Shipping Promotions
Free Shipping is for the contiguous 48 United States. For other locations, an accurate shipping quote is required. Oversized or freight items may not be eligible unless specifically stated.
Canada Shipments
Ground Shipments to Canada incur customs duties and taxes. The customer is responsible for brokerage fees, taxes, and duties. Failure to pay may result in product abandonment.
International Shipments
We offer international shipping. If our website does not initially support your location, contact us for a custom shipping quote. International customers are responsible for duties, taxes, and customs charges.
Not 100% sure this part fits your truck? We verify every fitment by hand — for free.
Call us at +1 (877) 898-0737 or email support@secondtruckparts.com with your VIN (or year, make and model) and the part number, and a real parts expert will confirm fitment before you order.
At Second Truck Parts, we guarantee the quality of our used heavy-duty truck parts with a 90-day warranty, starting from the purchase date, covering defects in materials and workmanship under normal use.
Exclusions: The warranty does not cover damage from accidents, misuse, negligence, alterations, normal wear and tear, improper installation, or maintenance.
To Make a Claim: Contact our customer service at support@secondtruckparts.com or +1 (877) 898-0737 with your order number and issue details. After evaluation, we will guide you through the process, which may involve returning the defective part. Note: customers are responsible for return shipping costs.
Terms: The warranty is non-transferable and void if installed by an unauthorized party. We reserve the right to repair or replace the defective part.
Thank you for choosing Second Truck Parts. For any questions, please contact us.
At Second Truck Parts, customer satisfaction is our priority. You may return any purchased part within 30 days of receipt for a full refund. Before returning any item, please contact us at support@secondtruckparts.com to receive a free return label via USPS in most cases.
All products must be returned in new, unused condition, with original packaging, and must be saleable. Returns must have a valid RA number issued by our customer service, and items that have been installed, modified, or are special orders and electronics are non-refundable.
Restocking Fee: A 20% restocking fee applies to all returns.
Return Process:
- Contact us for a Return Authorization Number (RA).
- Ship your return to our facility.
- Receive a credit within 48 hours after inspection.
For assistance, call us at +1 (877) 898-0737 (8 am - 8 pm EST) or email support@secondtruckparts.com. Thank you for choosing Second Truck Parts!
