Prado Cruise Control Problem

Submitted: Tuesday, May 04, 2010 at 20:40
ThreadID: 78228 Views:4384 Replies:5 FollowUps:3
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G'day Folks. My son's 2005 4.0 litre auto GXL Prado, has had a cruise control issue since new. A slight hill or headwind will cause the auto to kick down 1 or even 2 gears even at 110 Km/h or more. Unless it's a perfectly flat road or no headwind it's pretty much unusable. We think it may be a tuning issue but don't know how to adjust it...Any helpful hints welcome. Thanks
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Reply By: Member - Brenton H (SA) - Tuesday, May 04, 2010 at 21:00

Tuesday, May 04, 2010 at 21:00
Yep, mine does the same. Ok on the flat but if it has a 'catch up' to do say up a hill it really goes for it rather than a smooth progressive adjustment. Can be quite disconcerting especially if you are also on a sharp corner at the time.
AnswerID: 415415

Reply By: Member - Toyocrusa (NSW) - Tuesday, May 04, 2010 at 21:00

Tuesday, May 04, 2010 at 21:00
Hi Warren. The cruise is a bit finiky on the 5 speed auto. It does depend on how much weight the vehicle is carrying. The heavier the load verses the more the gradient and/or headwind the quicker the auto will drop out of lockup and 5th gear, especially at 110 kph. I have found running it in 4th does help. Not sure if the auto computer could be re programmed. Bob.

AnswerID: 415416

Reply By: Rangiephil - Tuesday, May 04, 2010 at 21:38

Tuesday, May 04, 2010 at 21:38
The cruise control is only trying to do what cruise controls do. The problem is the calibration of the auto and that is not something you can change easily if at all.

Can I suggest that you perhaps anticipate a hill that you think will cause the kickdown problem and accelerate in anticipation before the hill to get a "run up"

If it is like my cruise control it will not drop out if you put your foot down a bit.

The other thing you may be able to do if it is a cable cruise is to put a stop on the cable to reduce the maximum throttle applied to prevent it going into kickdown. Of course then you will slow down more than 10Kmh and the cruise will drop out which I find more annoying than kickdown.
Regards Philip A
AnswerID: 415425

Follow Up By: Member - Toyocrusa (NSW) - Wednesday, May 05, 2010 at 06:41

Wednesday, May 05, 2010 at 06:41
Definately not cable Phil. All elecronic.

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FollowupID: 685552

Follow Up By: George_M - Wednesday, May 05, 2010 at 12:20

Wednesday, May 05, 2010 at 12:20
That's what I do. When approaching a hill I click the criuise control off, accellerate slightly before I get to the bottom of the hill, and click the cruiise control back on when I get to the top.

For some reason you can use a particular throttle setting going up a hill and the transmission won't kick down, unless you're using cruise control.

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FollowupID: 685588

Reply By: HGMonaro - Wednesday, May 05, 2010 at 11:14

Wednesday, May 05, 2010 at 11:14
has been a bit of discussion about this on pradopoint. General concensus is that it is very agressive in it's endevour to maintain your speed, it's very willing to throws gear changes and lots of revs at the issue! No real drama as long as you don't mind the associated increase in fuel consumption and a bit of extra noise. It does it smoothly enough :)

I tend to suspend the CC and let it loose a few kph but stay in top gear. If I'm towing, I'll knock it back to 4th and do the same.
AnswerID: 415484

Reply By: Wherehegon - Wednesday, May 05, 2010 at 19:06

Wednesday, May 05, 2010 at 19:06
Common issue with all toyotas not just prados. I have an 01 prado t/d auto with factory cruise and now unless on level roads with very minimal hills I over ride the cruise. I find as it approaches a hill instead of feeding the power on slowly it thinks say in a 110 zone" mmm approaching a hill, mmm starting to climb a hill, oops I lost 5+ klms in speed, "BANG" down goes the throttle, kicks back one or two cogs, builds up the speed, oops now were going over the set speed,mmm better back off a bit while still holding out of overdrive, drops just under 110 drops back into overdrive slowy works itself out and all settled "till the next hill" sound familiar ??? My previous prado was exactly the same.Regards Steve M
AnswerID: 415541

Follow Up By: StormyKnight - Wednesday, May 05, 2010 at 19:41

Wednesday, May 05, 2010 at 19:41
Yep......this is right.....

Combination of low horsepower at low revs (tall top gear - 2200rpm @ 100km/h) means it can't hold the set speed even at full throttle. The auto has no option but to kickdown since thats how its programmed to a full throttle event at that road speed.

I guess if we would also complain if it didn't put enough effort in too :)

Getting an engine chip apparently helps, however it will need to be a pre-ecu type (Ditronic) rather than a post ecu type (DPChip) since the later uses a wire attached to the throttle to measure the intended load request to add power over standard engine output which the cruise can't provide since its all electronic.

The lighter you are the better behaved it is, but the heaver you are the extra effort in changing gear quickly can also be handy.

It would be nice to have a 2 mode system, so you could set it to "lazy" mode where it would cruise at 100, but under a certain amount of throttle it would aim for 95 or 90, but return to 100 when the road was flat again.

Anyway, its annoying, but not much I can do about it, I'm much happier with the tall final gear ratio than the cruise issues....

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FollowupID: 685634

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