Continuing to fix the electrical issues on my manual Vantage, I'm now addressing the reverse indicator.

While driving the car, at random speeds and in random conditions, the red reverse indicator will sometimes flash on the instrument cluster (accompanied by an audio bong and the parking sensors turning on for a second until the car realizes it's going forward at more than 10mph). It happens at low speed, at high speed, while cornering, while driving straight, while on bumpy roads, and while on smooth roads. The only way I can intentionally increase the frequency of how often it happens is by taking left turns.

There was only one other thread I could find regarding this issue and it was suggested that the reverse sensing switch located on the transmission is the culprit (which the workshop manual calls a reverse light switch, but doesn't have procedures to replace it). Part number 6G33-8F875-AA. It's probably just gotten sticky and doesn't always fully extend.

Astonmartinbits has it for about $160 plus shipping, so not too bad on cost. My question is this: has anyone replaced it without removing the transmission? Where exactly is it on the housing? I'd like to put the car on a lift and remove it to investigate whether it's repairable / un-stickifiable before buying a new one.

 

I find the parts diagrams on Scuderia very useful. Just search using the part number...looks like it’s external to the transmission, although there are several parts labeled #7 in the diagram.

https://www.scuderiacarparts.com/par...25207?h=192319

 

Yeah, I saw that earlier when I looked up the part. The diagram on scuderia doesn't show the switch. The one on astonmartinbits does, but it's not much clearer. And, of course, it's not called out specifically in the workshop manual.

I think I'll just put the car on a lift or jack stands this weekend and take a look myself.

 

Just ordered the switch from AMbits. I figured now would be a good time to buy it, considering Truss and her party killed the value of the pound sterling so badly it's almost 1-to-1 with the dollar, so £174 translated to only $195.

My condolences to the UK car enthusiast community for the prices you must be paying for petrol right now. Yikes.

 

You may also check your PDC sensors and wiring... this can cause the exact issues you're experiencing.

 

I did a bit of troubleshooting today. Put the car on a lift and disconnected the reverse light switch on the transmission (the switch is on the right side, forward, near the top, and is impossible to remove unless the transmission is dropped).

The wiring diagram shows that the switch provides a ground (or earth) to enable the backup light relay on the Central Electrical Module, which then sends power to the reverse bulbs, the reverse indicator in the cluster, and the parking aid module.

So, I disconnected the switch and drove the car a bit, and the reverse indication was still coming on randomly. Which means the reverse switch is not the problem. The upside of this development is that I don't have to drop the trans to replace the switch. The downside is that I now know that relay R2 on the CEM is engaging when it shouldn't be.

Two possibilities: either the wire that runs from the switch's connector to the relay is chafed and intermittently touching the chassis somewhere, supplying a ground to the relay; or the relay itself is not fully disengaging / sticky. Neither option is good.

Regarding the PDC module suggestion: I'm not sure if that is causing the issue, but I'll definitely keep it in mind when I'm troubleshooting. If that's the case it should go away if I unplug the module and drive the car, but I don't know where it is. Going to have to research that, too.