Mack Titan MP10 - Intermittent Throttle Response with MID 249 SID 29 Fault

Question

I am getting a weird intermittent dead pedal on my 2014 Mack Titan. The truck will be cruising fine then suddenly ignore all throttle input for about 5 seconds before kicking back in. I pulled the codes and I am seeing MID 249 SID 29 which points to the auxiliary throttle.

road_rambler · Accepted Answer

Found the issue at the frame rail harness connector near the transmission. There was a rub-through on the wire for the remote throttle prep package (even though this truck didn't have a PTO installed). The wire was grounding out against a bracket, sending a 0.5V signal to the VECU which triggered the SID 29 conflict. I repaired the wire, heat-shrunk the section, and re-secured the loom with stand-off clips. Total cost was just labor and 20 cents of shrink tube; has been 5,000 miles without a hiccup.

Greg Walters · Answer

On these Mack and Volvo setups, MID 249 is for the Vehicle ECU. SID 29 refers to the secondary or extra throttle circuit. If you don't have a PTO or secondary station throttle, the VECU might be seeing noise on a circuit it thinks exists.

Carlos Diaz · Answer

Have you checked the VECU parameters with Premium Tech Tool? You should look at the configuration for 'External Accelerator' or 'Remote Throttle.' Sometimes a software glitch or a bad ground makes the module think a remote throttle is being used when it isn't.

Megan Rivera · Answer

Check the harness connector at the firewall where the throttle signals pass through. Moisture intrusion in those pins can cause a voltage jump that the VECU interprets as a secondary throttle input conflict, causing it to go into a safety idle mode.

Mack Titan MP10 - Intermittent Throttle Response with MID 249 SID 29 Fault

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