Z4-forum.com

When we bought our 2003 3.0i auto with 43K last year the private vendor warned that the trans warning light would light up occasionally but just switch off and on again and it would go away. Well, we didn't have any issues for a few weeks after purchase but then on it came and limp mode was enabled, switched off and on again - all OK.

A month or so ago things got worse and at every start up the light would come on - something had to be done! A transmission oil and filter change seemed unecessary at such low miles but that was done by my local mechanic. Smoother change and a quiter transmission but the light was just as active.

Today I decided to have a look at a few connections below the car. The main multi pin plug on the transmission didn't have the lock ring fully seated so off it came for inspection. All the connections were clean so I reconnected it and locked it fully. A bit of waxoil on the brake pipes that I could see and a general look over while I was there.

So, start up, no warning light, drive to my brother's house to get keys, stop and start up - no warning light, drive to my nephew's garage to collect an OBD11 code reader, stop and start up - no warning light, drive to the petrol station for a fill up, stop and start up - again no warning light.

When I got in the drive at home I finally connected up the code reader. Two codes were recorded, one on the engine and the other on the auto trans. Enigne - P0701 - transmission range fault - signaling that there was a fault in the circuit that fed the transmission module. Auto trans code -P0709 - transmission range circuit intermittent - signalling that the circuit from the transmission range switch was intermitently faulty - a loose connection? Should have borrowed my brother's OBD11 reader earlier.

So, here's hoping that all that was needed was the connector reseated properly!

Did you reset the fault codes?
If they come back after re-setting then you know it's a problem more than re-seating the connector appears to fix, perhaps.
Prob a good idea to clean the connector contacts with some contact spray if they've been exposed to the elements to any degree?

Yep, reset the codes. The conections were bright and clean so I didn't spray them, just tightened everything up. Must not have been in close enough contact. We'll see if anything returns.

That's good news jimmy, I would have given the plug contacts a good squirt of electrical contact cleaner, just to be 100% sure. Fingers crossed for you.

No fault codes have returned, but the light has........ I cleaned the connector with switch cleaner, no improvement. My next investigation is the switxh itself. I read somewhere that it is possible to disassemble them and clean the contacts but can't find the post. A new switch appears to be expensive!

My Zed did the light thing about 4 times in 5 years. I'm sure I read somewhere that it's just a position sensor or something that causes it. I don't think it's usually anything too sinister.

Yes, It's the position sensor on our car, or the wiring to it. I've narrowed it down that far but the sensor is very expensive.... a secondhand one on ebay - £175 - no gauruntee and no returns! I saw a thread somewhere where someone dismantled one to clean it, just wondering if anyone could advise if it's sucessfull and how easy it is to remove before I tackle it.

1972nail wrote: ↑Sun May 21, 2017 2:43 pm No fault codes have returned, but the light has........ I cleaned the connector with switch cleaner, no improvement. My next investigation is the switxh itself. I read somewhere that it is possible to disassemble them and clean the contacts but can't find the post. A new switch appears to be expensive!

If the lights coming on there will be a fault code somewhere, the car knows it got an issue, hence the light and that event will be recorded somewhere. I would be tempted to have it scanned with some better equipment at an indie/specialist before spending any money/taking things apart to see exactly whats going on

Hopefully this is my final report on this issue.

The cleaning I did back at the beginning of May did improve the issue for a very short while, until the switch cleaner dried out.....about a week or so. The warning light issue never returned anywhere near as often or or severe as it had been prior to the contact cleaning so I held out some hope of it being just dry contacts, but the issue was gradually getting worse. So, a better contact cleaner and lubricant was purchased and the connector taken apart and cleaned 2 weeks ago. Result! ........ of a sort anyway.

But now, if the headlights were on and you shifted to Park, or if you had just raised the roof and shifted to Park then the warning light would appear. Hmmmmmm....... Loads of posts say that a failing or under powered battery can cause various strange things and it would appear that my problem had now been narrowed down to the battery not being able to supply enough voltage at critical times.

On investigation the original battery had been replaced by the previous owner for a 72 AH 670 CCA budget 096 size battery only a couple of years ago. So rather than take anything more apart for cleaning or replacement I decided to invest in a new battery. A bit of research narrowed the search down to a Bosch S5008 or a Varta E44, both 096 size and 77AH 780 CCA. There are other 096 ones from both manufacturers with slightly lesser specs but as these better ones were only a few pounds more, why take a chance? In the end my local motor factors had the Varta E44 in stock at a very competitive price, so that's what I purchased.

After an overnight trickle charge to make sure it was at it's best performance I fitted the battery this morning. Before fitting the new I did the test with the lights on and roof down and up while changing to Park and the transmission warning light came on consistently. After changing the battery....... no problems! The roof also reacted noticeably faster.

So hopefully my 'Tale of the Transmission Warning Light' saga is over and resolved with a suitably powerful battery and a clean of the inhibitor switch connections. I believe both had been contributing factors.

Mine does that too every now and again. I notice that if I put the keys in and turn the enigne on straight away sometimes the light comes on but if I put keys in then turn until lights come on the dash then put my seat belt on then start the engine it never comes on. Not worried about it too much

That's the way ours started, occassionally, then more often and then finally every time he car was started, Cleaning the contacts in the connector helped immensely but the final cure was a good battery.

Mmmm I'll have to keep an eye on it. At least it seems like an easy ish fix.

I bought GreyZeds car back in April (its a great car buddy) and the light started to come on more frequently on start up just as John has described. I took it to an indy and they detected that the altrrnator wasn't pumping out enough juice. Had it changed and (fingers crossed) no issues since.

Sorry for bringing up an old topic! But we are having an issue with our Z4 light coming on, we had it scanned and it was the P0709 code, Trans Range Sensor.

Where was the sensor located at on the E85?! I am going to clean it out, and see if that is the problem. We went on a road trip to Dallas, and went through ALOT of salt on the roads, and snow and ice, so I have a feeling it is really really dirty.

But to save my life, I have not been able to find a picture of where the sensor is, or any clues to what end of the vehicle it’s located at even!

Thanks a bunch.

austinboyette wrote: ↑Sat Feb 10, 2018 4:07 pmSorry for bringing up an old topic! But we are having an issue with our Z4 light coming on, we had it scanned and it was the P0709 code, Trans Range Sensor.

Where was the sensor located at on the E85?! I am going to clean it out, and see if that is the problem. We went on a road trip to Dallas, and went through ALOT of salt on the roads, and snow and ice, so I have a feeling it is really really dirty.

But to save my life, I have not been able to find a picture of where the sensor is, or any clues to what end of the vehicle it’s located at even!

Thanks a bunch.

Im sure someone will give you the info you’re after but in the meantime you could try having a look on realoem.com if you haven’t already.