code 42 on both mine and my buddies manual NA supras

[thedice917]

i heave searched and found nothing that helped me. my Supra was an Auto converted to Manual, i ran the Auto ECU for awhile with no issues minus a low idle stall problem. i swapped the ECU for the Manual ECU since a friend of mine needed the Auto one. since then i get a CEL and an Error code 42, no symptoms that i am aware of though. i was going to let it go until my buddy's car started doing the same. as far as i know his is not a conversion but a genuine manual. i checked his codes today and 42 was the only one. we are wanting to fix our cars but haven't been able to find anything for the manual cars.... on a side note, i have to have my idle set up to 1200 rpm to keep my car running at stops. i have cleaned the IAV and id did nothing... it also ops checked good. any input would be great!

[stevie_b]

Code 42

I'm assuming your speedo still works, as you said there's no obvious symptoms other than the warning lights. It's probably caused by the buffer circuit failing in the odometer unit. There are threads about that: I've posted in most of them.

There's a modification you can do to the odo which bypasses the buffer circuit. Or, you can replace yours with a known good odo unit, and get the mileage counter rest to what it should be for your car.

[Mike2JZ]

Typically code 42 references either a faulty speed sensor (located on gearbox) or a faulty/incorrectly wired KMH->MPH conversion box (black box usually located behind speedo)

 

There are other possibilities for code 42, but I'd check those two first.

 

Edit: You and your friend could swap ODO's to see if the issue is still present once swapped. If it is, you are either both really unlucky and have broken ODO's or you both have an underlying issue that needs sorting (my money is on underlying issue)

Edited November 5, 2015 by Mike2JZ (see edit history)

[stevie_b]

Typically code 42 references either a faulty speed sensor (located on gearbox) or a faulty/incorrectly wired KMH->MPH conversion box (black box usually located behind speedo)

 

If it's either of these, the speedo won't work.

[HarleyFDMD]

I developed fault code 42 it's pretty common. Remove the odometer and access the plug that plugs into the back of it. You then bridge two of the wires together (I found a guide on here which showed me which wires) then problem solved!

As mentioned its never usually the speed sensor. Dry solder on the odometer can sometimes cause it too which is also cured by bridging the wires if I'm not mistaken

Edited November 6, 2015 by HarleyFDMD (see edit history)

[Mike2JZ]

If it's either of these, the speedo won't work.

 

Perhaps for the speed sensor, but it does still work with a faulty conversion box, fixed one recently where the speedo still worked but was chucking out 42 code stil

[thedice917]

Even if the odo works as it should and nothing has been converted to MPH? Also, my light came on only after I swapped ECU's, it goes stays off after I restart the car for about 5-10 min. When driving. Then comes back on. I will check the odo anyway. I have a spare one