hardly worth mentioning
Crashes / Fires:
0 / 0
Injuries / Deaths:
0 / 0
Average Mileage:
51,000 miles

About These NHTSA Complaints:

This data is from the NHTSA — the US gov't agency tasked with vehicle safety. Complaints are spread across multiple & redundant categories, & are not organized by problem.

So how do you find out what problems are occurring? For this NHTSA complaint data, the only way is to read through the comments below. Any duplicates or errors? It's not us.

2003 Mitsubishi Diamante engine problems

engine problem

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2003 Mitsubishi Diamante Owner Comments

problem #5

Apr 112010


  • 60,000 miles


The contact owns a 2003 Mitsubishi Diamante. The contact stated he noticed an unusual odor of coolant and the neutral indicator began sporadically illuminating. Upon further inspection, the contact found coolant leaking onto the floorboard. In addition, the vehicle would intermittently fail to start. The dealer performed a diagnostic test and determined the failure was caused by the a.T. control relay and produced code P1751. The vehicle was not repaired and the VIN was not available. The failure and current mileages were approximately 60,000. Updated 10/27/10.

- Westerville , OH, USA

problem #4

Nov 012008


  • 60,000 miles
TL- the contact owns a 2003 Mitsubishi Diamante. The contact stated that the neutral light on the vehicle started flashing on and off and he noticed a smell of coolant. He noticed that the coolant was leaking onto the floorboard of the vehicle. The failure progresses until the vehicle will not start. The vehicle was taken to a dealer and the owner was advised the failure was the a.T. control relay. Code P-1751. The failure has not been repaired. The current and failure mileage is approximately 60,000.

- Westerville , OH, USA

problem #3

Jan 012010


  • 62,000 miles
I have a 2003 Mitsubishi Diamante with 60,000 plus miles. For the past several months I have noticed a strong smell of anti-freeze coming from the vents and the windows constantly fogging up, sometimes to the point that I cannot see to drive. I have read many similar complaints and agree with others that Mitsubishi needs to issue a recall for the heater core, as I am sure this is the problem. I have yet to take mine in to get it repaired, so I don't have a cost quote at this time.

- Knoxville, TN, USA

problem #2

Nov 052007

Diamante 6-cyl

  • Automatic transmission
  • miles
2003 Diamante issues. Started smelling a syrupy type smell, coolant smell throughout the cabin and had fumes escaping through the vent in the car. Coolant level dropping with no visible signs on the ground. Looks to be the heater core. Nothing has been done yet. Seen multiple complaints regarding the same issue and on this site. Wondering why so many complaints have been sent, but nothing done yet?

- Nashville, TN, USA

problem #1

Jan 192007

Diamante 6-cyl

  • Automatic transmission
  • 73,000 miles
On Friday, Jan 19, 2007, I went to my 2003 Mitsubishi Diamante vrx after work to go home. When I got to it, all windows were totally fogged over, which is abnormal. With high heat, I was able to clear a portion of the windshield, relying on a paper towel to clear the remainder. I parked the vehicle for about 2 hours after arriving at home and had to rely on paper towels to clear the windshield once again. This time, I noticed a distinct antifreeze smell. The following day, the sunlight showed the film to be of a green color. At this time, I realized that the windows weren't foggy, but it seemed that antifreeze vapors were blowing into my car. After some research on the Diamante owners' group website, it was evident that the heater core or O-rings were causing this. I took the vehicle to lawson Mitsubishi, where it is being repaired. This is something that happened with little identifiable warning. Had this happened on the road, an accident would have surely ensued.

- Lawton, OK, USA

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