CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Toyota "Limp" mode?

Does Toyota (2006 Sienna minivan) have a limp mode when there is something wrong with this car? A friend asked me to help charge their car battery. Their Uncle (who speaks little English) had a hard time conveying to me the exact symptoms, however, after we did get the car started it had a “check engine” light on and went into some kind of limp-home mode where the car will only go about 5mph.



When I got to the car, it had a voltage of 10V. I hooked up a spare battery (for occasions like this) but had the +/- reversed. I corrected the hook-up and the car still would not start but the starter would turn the engine about a 1/2 turn. I then hooked up my running car, and started the Toyota Sienna. When the car started driving it was in a limp mode. Did we damage a computer somewhere?



I have charged the battery, which is holding a charge, but can’t get out of the limp mode; if such a thing exists.

If you reversed the polarity there’s no telling how much damage might have been done.

Many vehicles have a “limp mode.” Time to read the owner’s manual.

It may (may not) make a difference whether the ignition key were turned to ON, or not, while the jumper cables were reversed. Even with the ignition key OFF, there is still a “keep alive” voltage to the engine computer. Is this “keep alive” circuit resistant to damage to the engine computer from reversed polarity (from reversed jumper cables)? I don’t know.
Hopefully, someone who knows the internals of the engine computer will show some light on this question of reversed polarity effects.

The ‘limp mode’ refers to a faulty transmission.

Just about all vehicles have this programmed in.

It’s to allow you to ‘limp’ to a tranny shop for repairs.

It effectively prevents the tranny from shifting past 2nd gear.

Get the van to a tranny shop and have a scanner hooked up to find the problem.

Good news! It turns out that hacks like me benefit from one of the most important electrical part in the car… the fuse. Thank god, the cheapest part in the car protected me from destroying the most expensive part in the car. In fact the part didn’t even cost me a penny thanks to my practice of junk yard fuse pulling; I never leave the junk yard without a handful of fuses.

Special thanks to “mcparadise” for telling me to read the owner’s manual; by fate I landed on the fusebox page, and entertained myself by looking over the fuse labels and found “ETCS” which had to stand for Electronic Traction Control System. Faster than I remember, I pulled the 10A fuse for ETCS and the biggest smile covered my face when I found it had been FRIED!

Moral of the story… Electrical problems should always start with Step 1: Check your fusebox.
Moral of the story II… Transmission limp-home mode problems should start with Step 1: Check your ETCS fuse!

Good to know, happy ending. Lesson number one though should be, check the leads like ten times before jumping a car!

Hey Carhack,
Thanks so much for posting your resolution here, I did the exact same thing on my 2011 Sienna, same symptoms (loss of power, VSC light, check engine light on, . Had completely zoned out when attaching the cables (but who puts a black cover on a positive terminal?? they do on a Tundra which was my jumper vehicle). Anyway i still chalk it up to my stupidity, no way around that. But yes, that ETCS fuse was blown (I would not have thought to check that specific one, the VSC fuses were all good, the ECS fuses were good, the 140a fuse was good, I was about to give up but saw your post, checked it and all good!!! There was even a spare fuse in the box (thanks Toyota :slight_smile:)

Much appreciated!!!

1 Like

The last response to this thread was 11 years ago…

Yes it was, but does that make the post any less relevant or make me appreciate it any less? Not in my opinion.

Just letting you know… lots of people do it.