17th Aug 2008, 20:27

To PO403 Problem:

PO403 is code for EGR Control Circuit. PCM checks for current flow in EGR solenoid drive circuit. IF solenoid voltage does not reach present limit during engine starting, then code is set. You've already taken step to replace EGR solenoid, so can scratch that off the list of possibilities. Next most likely culprits are short or ground in the wiring, or a loose connector between EGR solenoid and PCM (Power train control module). You'll need voltmeter and toubleshooting guide to solve this. I strongly suggest you subcribe to on line shop manual service as it will save you much frustration and money to solve some these problems yourself. Good luck.

Marco in Indy.

25th Aug 2008, 01:18

I just bought a 02 diamante ls and took it back the next day because of the drive and neutral alternating problem. After reading this thread I definitely would like to bypass the heater core (which I did smell anti freeze). Can someone please give a somewhat detailed "how to" so I can do this bypass when I get the car back. Thanks.

Mike in California.

15th Sep 2008, 13:40

Peace, I have a 2002 VR-X and I have had problems with the heating coil, which I had replace while under warranty. But now I have the TCL light flashing, and it won't go into gear, nor will it rev up when the gas is pushed. Judging by what I read, it's a sensor of some sort, but what sensor is it? Can anyone help?

15th Sep 2008, 14:53

Just 2 months ago my daughter bought a 2002 Diamante, and amazingly she is having all the same problems. Brought the car to Mitsubishi because the transmission is acting up. It seems to shift with a jerk, but if you let up on the accelerator, it will shift smoother. Dealer said heater core is leaking. ($1100.00).

Also, they could not tell if problem is in the transmission or from a bad computer. First they would look in the transmission (I think he called it the valve body- $1800.00) and if that didn't fix it, they would replace the computer ($2000). I asked him if the leaky seal could have caused the computer to go bad and he said "no". Can you believe that? Then I come home and do some research and read all this. And of course the TLC light is flashing from a bad sensor ($600) and the antenna doesn't work. Unbelievable!

I see I can buy a used ECU for $125. Does anyone know if that is something you can install yourself? Also, could anyone venture a guess whether my problem is the valve body or the ECU? The transmission has been doing that for about a month now and doesn't seem to be getting any worse. Any help would be much appreciated. My daughter just got married and bought this car. She certainly can't afford a $6000 repair bill.

17th Sep 2008, 09:56

I have a 98 Diamante; heater core leaked after 70k miles and went to dealer and replaced for $950. Now it is leaking again after 40k miles more, so they obviously used the same bad gaskets from the factory. This is a joke and Mitsubishi should flip the bill for using these poorly designed gaskets to begin with.

I filed a complaint with the NTHSA; any lawyers on here so we can file a class action lawsuit?

3rd Oct 2008, 21:00

Parting out 2002 Diamante LS, what do you need? It's cheaper to sell off the parts than fix it!

5th Oct 2008, 20:41

Regarding the 02 VR-X issue with dealer saying either transmission or PCM (Powertrain control module) is causing the shift problem, I bet it's the PCM. Why? Due to a leaking heater core. I'd just repaired my own leaking heater core on a 02 VR-X by replacing the heater core pipe gaskets. No I didn't have to take the entire dash out like the dealer wants to do for $1000+. I got to it from behind the glove box with a procedure I found online.

Anyway, when I got to the heater core, I could see that it had leaked onto the PCM that is located just below the heater core - bad design MIT! While there was a plastic sheet over the PCM, I could see if enough antifreeze had leaked out, it could create enough moisture and corrosion in the PCM. I think that if you pay some young mechanic $500 to replace both the heater core pipe gaskets & PCM at the same time, your major issues are solved for a reasonable cost.

Your ABC/TCL light is another issue I recently had, and solved for less than $200, but that's another story. Good luck!

7th Oct 2008, 12:09

I have a 2002 VR-X with 100,000 miles on it. Have not replaced the timing belt yet. Is there anyway to tell if it is close to going??

Also, I used the tablets for leaking radiator and it worked.

8th Oct 2008, 17:58

Yes, when the belt breaks and you're stranded and engine is damaged! You are definitely due for timing belt change at 100K. Not worth the risk. As they say, pay me now or pay me much more later.

Also have water pump replaced at same time. They tend to crap out around this mileage. Since the water pump has to be removed anyway for the timing belt change, you've already paid for the labor, which is most of the repair $$.

What tablets are you referring to, and what type of radiator leak did you have?

9th Oct 2008, 01:39

I have a 2002 Diamante I purchased in '05 with 67,000 miles. First week I smelled anti-freeze, had window fogging and wet carpet. I went to auto parts store and bought radiator stop-leak, put it in filled with anti-freeze and guess what? No more problem with leaks, now at 100,500 miles and still no leaking. Antenna did need to be replaced at 95,000 miles and brakes pads at 100,000 miles. The check engine light just started to come on a couple weeks ago, and it didn't pass smog because of 02 sensor (P0154) - (P0401) EGR Flow Insufficient. Going to fix myself if possible.

18th Oct 2008, 23:15

I just purchase a 2002 Diamante LS 4 months ago with 72000K and I believe I'm have the same heater coil issue, but there is a difference. I have no leak nor antifreeze smell, but my heat is blowing out cold air. I have 83000k on the dash now. Can someone please let me know what this possibly could be so I can find an affordable route to fix this ASAP; it is 40 degrees today!!!

23rd Oct 2008, 09:24

I too have had the infamous heating core problem. 2002 Diamante with 79,000 miles. I urge all of you to file a report with the website listed earlier. Here it is if you missed it the first time.



28th Oct 2008, 11:20

Can anyone tell me what to do about my TCL light flashing? I know it has to be a sensor but don't know where, what, or how?

28th Oct 2008, 12:09

Has anyone had a problem with the "TCL" flashing? I have a 02' Diamante and I believe it's a sensor of some sort but do know which, what, or how to fix it? Can anyone help? Yahdeenyahdeen@yahoo.com.

28th Oct 2008, 13:38

I have 2003 Diamante LS and the heater core is still leaking after I replaced it at the cost of 670.00 labor and parts. The problem appears to be common on this car. I will not buy another one.