Flashing ATP & 4WD Mode lights

Sammy · Nov 17, 2019

On a recent trip towing the caravan I suddenly lost drive power (like engine revving and not connected to the transmission) and the ATP & 4WD Mode Indicator lights began to flash. I pulled over and let everything cool down for about half an hour. Restarted ok, drove another hour into Longreach, had transmission fluid flushed and replaced then drove home gently to the Gold Coast. This was the best the mechanics could do but did not really know the cause. Am not sure I feel confident in it not happening again. Any ideas will be appreciated.

Old.Tony · Nov 18, 2019

It's not a problem that I've experienced, but at a guess I'd say the gearbox may have gotten a little hot. This thins the oil, and if the TCC disengages it will slip a lot more.

Find an automatic transmission specialist. Not a backyard 1-2 guy operation. Look for someone with 5-6 workers minimum. Have the guy hook up his diagnostic tool and take the car for a drive. He'll be able to tell you if the gearbox is performing normally.

Also, you might consider having an external transmission cooler fitted. I had one fitted early on - I now have two - and never have any problems with power delivery. I've had issues with vibration (worn TCC) and a total bodge job by the mechanic from a small shop that completely rooted my gearbox so I had to buy another, but she's never gotten too hot.

I am quite particular about keeping my coolant temp below 105C, even though (unlike the original) my transmission cooler is no longer in the radiator core. Keeping my engine coolant temp down means I'm not loading the drive train too much and the gearbox stays at a nice temp and never gives me trouble.

Engine: 327,000km. Towing: about 150,000km.

Sammy · Nov 19, 2019

Very much appreciate your advice Tony. I really like driving my D40 and I suspect you are spot on - the only missing link was that I did not get any "AT OIL TEMP" light that I recall. Though I guess this could also have come on as things were happening fast at the time. I will definitely take it to a reputable automatic transmission shop to have it fully checked out. What ballpark cost would I be up for getting the extra AT cooler? Cheers.

Sammy · Nov 19, 2019

Couple of afterthoughts Tony. What is the TCC? Coolant temp below 105C - is that engine or transmission? DO you have a thermometer readout in the cabin? Did you change your engine radiator also? Pls excuse all the extra questions!

Old.Tony · Nov 21, 2019

I think my larger cooler cost about $300, it's the one you should consider because the little ones like those that Supercheap sell won't really do much. After that it's mechanic's labour costs. There are two hoses running from the transmission to the bottom of the radiator, these come off the radiator and onto the new cooler. Block off the radiator pipes that the hoses came off, job complete.

The TCC is the Torque Converter Clutch. This locks the torque converter onto the driveline so there are no lost RPM (no slip).

Coolant temp is the engine coolant. If your engine is getting hot, so's the rest of everything (heat comes from load).

I use an app in my in-dash Android system and one of the sensors we monitor is engine coolant temp and I have set up an alarm for when the coolant temp reaches 104C.

And while I have changed my radiator, it's been replaced with an aftermarket identical unit, not an "improved" one.

KevinE · Nov 22, 2019

Sammy said:
On a recent trip towing the caravan I suddenly lost drive power (like engine revving and not connected to the transmission) and the ATP & 4WD Mode Indicator lights began to flash. I pulled over and let everything cool down for about half an hour. Restarted ok, drove another hour into Longreach, had transmission fluid flushed and replaced then drove home gently to the Gold Coast. This was the best the mechanics could do but did not really know the cause. Am not sure I feel confident in it not happening again. Any ideas will be appreciated.

The reason that you lost drive power is that the transfer case went into neutral. That's what it means when the ATP light comes on. That's also why the 4WD lights flashed, the car was effectively not in 2H, 4H, or 4L. it was just rolling along in neutral, because the transfer case wasn't operating. A fault in the 4WD system causes it.

My understanding is that a simple re-start will get you moving again, but if you haven't located the fault, chances are it'll happen again.

If you have AT temp concerns, I'd buy yourself a scan gauge & monitor what's going on in the AT & coolant temps. I don't know how you tow, but auto's don't like to be left in D while towing heavy loads. If you use sports shift & stay away from overdrive while towing, your AT will thank you for it.