WASHINGTON (WUSA9) -- DC Fire and EMS say they know why an ambulance shutdown while transporting a critically injured patient last Wednesday.
They are saying it was not the emissions system that shut down the engine, instead it was a mechanical problem.
A third of DC's newer ambulances are being brought to a Hyattsville mechanic shop to prevent what happened last week.
A faulty coolant screen triggered the engine to power down.
The mechanical problem happened with Ambulance 19 that was carrying carjacking suspect, 34-year-old Nathaniel McRae who was shot by police.
The ambulance was stuck on 295 while another ambulance transported the patient, costing 5-7 minutes in response time.
Deputy Chief John Donnelly, DC Fire and Ems said, "The engine was powering down, she did exactly what she was supposed to do and get it safely off the road."
After investigating the problem with the manufacturer, International/Navistar, Deputy Fire Chief John Donnelly says the problem was not part of the emissions system, as they first thought.
"This was not a regeneration problem, it was another component giving the power down signal," he said.
The component is a screen the size of a thimble that will be removed from the fuel system.
As a precaution 32 of their newer model ambulances, about a third of their fleet, will get the screens removed and get computer software updates.
The deputy chief says they are still confident in these ambulances. He said, "This current fleet we have is our work horses. They're going to be our future. They're good ambulances."
9 of the 32 ambulances that need fixing have already gone through the mechanic shop.
DC Fire says it only takes 20 minutes for each vehicle and they're doing it during their down time.