Hi guys,
My '02' 3.5L magna executive V6 goes into limp mode (but not all the time) at the moment and i can't work out why..
I have reset the computer, cleaned the switch on gearbox, checked all fuses, lights cruise control, etc. everything works but something is obviously throwing it into limp.
But, it works brilliantly when it isn't in limp mode. Ie: when i start it, it either goes into drive fine and works properly for the entirity of the trip til i turn it off, or it'll clunk into reverse and throw it into limp straight away. The neutral button flashes once per second in limp and i only have reverse and 3rd. But it doesn't go 'limp' everytime i drive it...

I'm thinking i need to check my heater hoses and see if my ecu is wet maybe (from reading other posts)?? Any help would be appreciated and i would like to know if i have to pull the dash out to get to the ecu/heater hoses or if there's an easier way to get to it?

Oh, and just to add... I paid a mechanic for 3hrs labour (@155/hr) for a diagnostic on it and he said it was the relay switch. If it was the relay switch wouldn't it just never work??? And ive checked the relay switch and it's fine

I was taken for a $460 ride and spun a whole big story on how he had to pull the dash out blah blah blah, only to get my baby home and see that no-one had even touched the dash...

Hmm, clunking into reverse reminds me of how the transmission died in my old KS. It turned out to be the diff and was left too long which eventually took out the transmission. Mine also occassionally went into limp mode until one day it just died completely and ended up on a flatbed to the local dealer for a new transmission.

Well the ecu isn't wet, it's already got a plastic cover and my hoses aren't leaking... Back to square one.

Plz help, i can't afford another car and if my beloved maggie is too buggered i would be devastated. I love this car so much!

It is either the ECU playing up, coolant on the ECU or the relay has had it. The ECU relay is bolted to the side of the ECU and you should really start with this. You dont need to remove the dash to do the relay but the side cover has to come off hte drivers side to get access to it

Is the relay hard/expensive to replace? Or should i get an ecu from a wrecker and swap it out? There's no coolant on the ecu at all. Just had the driver side carpet pulled back to check all that too. How will i no if the relay is buggered?

If you change the ECU, you need to change everything.

The relay may be ok to test but is old and dropping out. First get a new one and repalce it as it is a cheap part and good way to ensure that you dont go further and end up being the cheapest part. It is a tiny black box with a 4 pin plug.

Check the diagnostics as follows:

If the control relay voltage is less than 7 V after the ignition switch has been turned to ON, it is judged that there is an open circuit or a short-circuit in the A/T control relay earth and diagnosis code No. 54 is output. The transmission is locked into 3rd gear as a fail-safe measure, and the N range light flashes at a frequency of 1 Hz.

To test the relay, unplug it and do the following:
1. Use jumper wires to connect terminal 2 to -ve of battery and terminal 4 to +ve of battery.
2. Check continuity between terminals 1 and 3 when:
a. both terminals 2 and 4 are connected to the battery.
b. when either 2 or 4 are disconnected.

Result:
There should be continuity between 1 and 3 in step 2a and no continuity between 1 and 3 in step 2b.

Issue is often this relay may drop out when hot so test may not be accurate

Got the relay out. Goin to get a new one in the morning, hopefully this fixes the problem.

Oh, just wondering if ive possibly done damage to any gears or clutch by driving it in 3rd? I never floored it from standstill (poor suckers behind me woulda been cranky), just eased off the mark, but i did have to drive it in 3rd around town close to 20 times and did 4 trips of highway driving (1hr round trip each time). I hope i haven't buggered it in that respect. :(

New relay... My maggie hasn't missed a beat! 14 bux well spent so far. Thanks so much for all the help guys :)

Congratulations!
Mechanic was right, I wonder why he didn't change it while he was in there?

/dumb question alert.

The ECU controls the relay, but what does the relay control?

/end dqa

Coz i told him not to. He wanted $1200 for the part and labour to fit it! And changing it out only took me 20mins and 14 bux, so i'm very glad i didn't let him do it

Coz i told him not to. He wanted $1200 for the part and labour to fit it! And changing it out only took me 20mins and 14 bux, so i'm very glad i didn't let him do it

You should let him know...

Hi, having the same trouble with my 03 TJ magna. Transmission clunks into reverse sometimes and when I'm driving occasionally the neutral light or park light comes on when i'm in drive. Just wondering where the ECU relay is and if you think it would help to change it. Thanks

if you are not sure then pm madmagna to help you.

can someone tell me where the hell to get one, litterally nothing but forums come up when i search about the relay??

What a transmission relay, most wreckers have third gen magna's and all Auto Magnas have relays

Congratulations!
Mechanic was right, I wonder why he didn't change it while he was in there?

/dumb question alert.

The ECU controls the relay, but what does the relay control?

/end dqa
I believe it switches power on and off to the AT solenoids, for the purpose of engaging limp mode when necessary.