Bought Car With Sensors Fitted In Rear Bumper But They Don't Work&

[Rodmac51]

Hi, i'm new to this forum and in need of some help please.

I've just bought my first Toyota, a 2005 Avensis T4, which has 4 rear parking sensors fitted to the bumper but there's no warning sound when reversing. I'm not sure if these are genuine parts or not but they are a perfect colour match to the bumper. If factory fitted are they wired up to all models or are some just left as blanks if the original buyer didn't take up the option when the car was new?

I can't find any cables coming into the boot but it seems a bit pointless if Toyota fitted dummy sensors to the bumper so I feel sure they ought to work!

Does anyone know if these should work and if they should how do I find out what's wrong with them? I guess if they should work there ought to be a bleeper somewhere, but I can't find one. Any idea where it might be fitted?

If they're not supposed to work on this model would I be able to remove them and fit an aftermarket set?

Any help would be appreciated please.

[Raistlin]

Hi, Welcome to the club... Enjoy

This shows how to wire it so you can see the loom and control box.

[Scoobs]

Might be a daft question, but have you checked to make sure the sensors aren't switched off. There will be a small switch in the boot that enables/disables the sensors. It's so you can disable the sensors if you're towing something.

[Rodmac51]

Thanks for the replies.

Scoobs - I haven't noticed a switch. Where's it likely to be located and how small is 'small'?

[korat102]

Toyota's favourite place for these switches seems to be behind one of the rear light cluster panels.

Have you checked the fuses as well?

[FROSTYBALLS]

Toyota's favourite place for these switches seems to be behind one of the rear light cluster panels.

Where you have a reversing light on one side only, the switch is often near the light cluster containing reversing light.

[Rodmac51]

Toyota's favourite place for these switches seems to be behind one of the rear light cluster panels.

Where you have a reversing light on one side only, the switch is often near the light cluster containing reversing light.

Thanks for your help.

It does have only 1 reversing light but there's no sign of a switch anywhere. However, there's a red wire going into the reverse light cluster which is possibly the connection to the sensors but I've only had a quick look and can't see exactly where it joins. I'll take a closer look when I get time but if that's the right cable it at least indicates they're wired up and should be working.

The reverse light works so I doubt if it's a fuse. I can't find any reference to a separate sensor fuse in the manual either. Is there one and if so where's it located?

[korat102]

Look for an inline fuse on the power feed. If you trace that red wire back a little, you should find a little fuse holder attached to it. Also, if you can find the control unit (probably in the boot behind a panel somewhere or under the floor) make sure all the connections are clean and secure.

[Scoobs]

The switch on mine is just below the parcel shelf on the left hand side. It's about the size of a penny piece and coloured the same as the trim, which makes it easy to miss.

[Rodmac51]

Thanks everyone but there's been a development....the car nearly caught fire!

On the left side there's a flap to access the light cluster. I was reaching through this to feel where the red wire went and was jiggling it around a bit to see if it was loose when smoke suddenly started to come from behind the boot lining. Panic ensued....I had no idea how to remove the lining so the only thing I could think of was to cut the red wire as I figured this must be the only live cable. The smoke stopped....... phew!

Anyway, I managed to remove the lining (more bits had to be removed than I expected though) and I discovered it was definitely a Toyota original part (it had the name & part no on the control box). I also found there was an in-line fuse which amazingly hadn't blown but there definitely wasn't a switch anywhere, nor any cable that could go to one.

So now I'm left wondering which part is shorting out and why did it happen with the ignition off? The cable to the reverse light can only be live with the ignition on? At least I know where everyhting is now and where it should go - I just need to find where the short is.

Thanks for the help so far. I'll report back with my findings (if the car hasn' gone up in smoke).

[skcollob_ho]

I bought my BiL's '06 estate a few months back and encountered similar problems. I couldn't find the switch either. I pulled out the plastic side panels underneath the boot trim, and behind the N/S/R wheel arch, in a few inches of water [a whole other design fault story there], I found the control box.

I found the following website very useful, and perhaps you might too. It has installation manuals for the parking sensors, so you can trace back all the wiring and find faults.

www.toyota-tech.eu [i did try to paste the direct links, but for some reason this site wouldn't let me, perhaps I don't have enough posts yet]

Hover the mouse over the 'Repair' tab at the top, then click 'Accessory Installation Manuals'. Simply pick your vehicle from the drop-down menus, and wallah!

Good luck.

[Rodmac51]

skcollob_ho, thanks for the info, which was very useful.

I'm a little confused now though. The manual seems to indicate the Avensis parking aid is for both front and back and the installation goes into the dashboard. Mine however is only at the rear and all wiring and components are stuffed behind the left lining in the boot. Perhaps they provided rear sensors only but didn't produce a separate manual?

Nevertheless, when I reconnected the wire I pulled off when the smoke started it started smoking again. As i had the lining removed this time i could see it was the control box - so I assume this is where the fault is. My local dealer quoted £70 + VAT for this unit which considering you can get a complete kit for less than £25 seems a bit steep. However, unless someone can say for certain that any other control unit will work I'm left with either buying the Toyota part or ripping it all out and fitting a cheap aftermarket kit. Not keen on this idea though, firstly I'm not sure if a different set of sensors will fit the holes in the bumper and secondly cheap normally means trouble at some point!

I'm beginning to wish I hadn't started this now but being a stubborn sod I'll have to resolve it somehow.