AI Damage2003 Mitsubishi Diamante: common problems
Owners of the 2003 Mitsubishi Diamante filed 56 complaints with NHTSA, most often about visibility and engine and cooling. Details by component below, with sources.
Key figures
- Owner complaints
- 56
- involving a crash
- 1
What fails most often
- 1 Visibility 50% of all complaints
- 2 Engine and cooling 30% of all complaints
- 3 Powertrain 7% of all complaints
- 4 Service brakes 7% of all complaints
- 5 Equipment 5% of all complaints
- 6 Suspension 5% of all complaints
- 7 Tires 5% of all complaints
- 8 Electrical system 4% of all complaints
- Visibility: 28 complaints (50% of all).
- Engine and cooling: 17 complaints (30% of all).
- Powertrain: 4 complaints (7% of all).
- Service brakes: 4 complaints (7% of all).
- Equipment: 3 complaints (5% of all).
Engines and transmissions
US-market versions per EPA. On the right: how many NHTSA complaints name this engine or transmission type.
- 3.5 L · petrol · 6 cyl
- automatic, 4-speed
Drive: FWD
Symptoms owners describe
How many of the 56 NHTSA complaints mention each symptom (automatic count from complaint text; one complaint can mention several).
Components owners complain about
| Component | Owner complaints | involving a crash | Technical service bulletins (TSB) |
|---|---|---|---|
| Visibility | 28 | 0 | 0 |
| Engine and cooling | 17 | 0 | 0 |
| Powertrain | 4 | 0 | 0 |
| Service brakes | 4 | 0 | 0 |
| Equipment | 3 | 0 | 0 |
| Suspension | 3 | 0 | 0 |
| Tires | 3 | 0 | 0 |
| Electrical system | 2 | 0 | 0 |
| Fuel system | 2 | 0 | 0 |
| Air bags | 1 | 1 | 0 |
| Exterior lighting | 1 | 0 | 0 |
| Latches, locks, linkages | 1 | 0 | 0 |
| Parking brake | 1 | 0 | 0 |
| Seats | 1 | 0 | 0 |
What owners report
Short excerpts of NHTSA complaints in the original wording. These are owner statements not verified by NHTSA; personal data removed.
Air bag did not deploy in 55 mph direct front end collision.
Tl* the contact owns a 2003 mitsubishi diamante equipped with cooper cs3 tires (na). While driving 25 mph, air from the vehicle's front driver side tire began to be released. The contact pulled the vehicle into a fuel station/repair shop where the tire was replaced.
The contact stated that the heater core fluid leaked onto the central computer and caused the transmission to fail. In addition, the gear shifter could not be released from third gear. The vehicle was not taken to the dealer. The vehicle was not repaired. The manufacturer was made aware of the failure.
Days later the front windshield started fogging up while driving and after turning the car off (whether it is warm or cold outside) I googled why would this happen and have spoken with a few mechanics and they are telling me that it is the heater core going out, and that the reason why my husband is getting light…
Tl* the contact owns a 2003 mitsubishi diamante. The contact stated the vehicle was consuming excessive amounts of fuel and she was concerned the vehicle would prematurely run out of fuel while driving.
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. Rd
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.
All diamantes need to be recalled and the heater core and/or its o rings fixed or replaced. If this doesn't happen, people will die when they suddenly cannot see the road through their front windshield. [xxx]
When owners complained
NHTSA complaints by filing year. The peak shows at what age the problems show up most.
Comparison
By complaint count this model year ranks 5,040 of 36,656 model years in the NHTSA data (top 14% most complained about).
On average one model year of the Diamante has 42 complaints (12 years in the data). This year has 56, above average.
What to check before buying
- Visibility. Wipers, mirrors, defrosters, cracked glass.
- Engine and cooling. Radiator and fan after a frontal hit, coolant level and condition, overheating.
- Powertrain. Shift quality under load, harsh shifts, transmission codes, CV joints.
- Service brakes. Pedal feel, ABS operation, leaks, discs and hoses.
Other years of this model
Questions and answers
What are the most common problems with the 2003 Mitsubishi Diamante?
Owner complaints to NHTSA most often mention: visibility, engine and cooling, powertrain. Total complaints: 56. The most frequent symptoms in complaint texts: A/C or heater (59%), windows, sunroof (34%), vibration (16%).
How many service bulletins (TSB) were issued for the 2003 Mitsubishi Diamante?
NHTSA lists 0 manufacturer service bulletins for this year. A bulletin tells dealers how to diagnose or fix a known issue; it is not a recall.
Should I buy a 2003 Mitsubishi Diamante from a US auction?
Owner complaints describe defects, not crash damage. Before bidding, check the components listed above and review the lot photos: VinWind builds a report of visible and hidden damage by VIN.
Other 2003 models
Read also
Sources: public NHTSA data (USA): service bulletins and owner complaints; YouTube: links to videos credited to their authors. Complaints are owner statements not verified by NHTSA, and describe defects rather than crash damage. Data updated 2026-11-05.