MAP Sensor Wiring Advice

JefferiesFarnol · 11th August 2021, 18:32

Hello chaps,

I have a question since I got my new 75 Tourer 1.8 back (at last) from its first MOT after being stored in a garage by the previous owner since 2016.

The only major thing that needed doing was a new catalytic converter but I wasn't overly satisfied by the garage I took it to since they kept it for two weeks and when I needed to collect it, they said that an engine light was staying on because they replaced the MAP sensor. Apparently it already had an after-market one which was spliced to the existing cables and so they did the same. They said that the problem was that the wires weren't matched properly and they couldn't get it right without a wiring diagram but then said they could 'order a sensor with the plug' so that it wouldn't need to be spliced which would cost about £100.

You might gather from that they aren't the best garage in the world. I left saying that I would take it back at some point for that to be done but I think it's the sort of thing I could do myself. I've really no experience with cars but I am a 'dab hand' at most practical things.

It seems to me that the plug that attaches to the MAP sensor is part of the wiring loom and so you'd have to change that in its entirety to avoid any splicing. I suppose the other alternative is to splice it properly.

I've attached some pictures and any advice will be much appreciated.

(As a side note, is anything supposed to be attached to the circled bracket in the third picture?)

Yorkshire GOC · 11th August 2021, 18:53

I cannot give you an answer but all MGR 75/ZT wiring diagrams are on the MGR RAVE disc which may help you or your garage.

https://www.ebay.co.uk/itm/263709186...QaAlHtEALw_wcB

Yorkshire GOC · 11th August 2021, 19:38

And welcome to the fold by the way

WillyHeckaslike · 12th August 2021, 05:08

The missing part regards the circled bolt hole is a heat shield. It might have been deleted by Rover 2001 as part of project drive but not certain. Regards the map sensor, not sure why they would touch it and what the problem would be given that all 4 wires are colour coded and any splice should be connected like-for-like. Maybe they mean the Lambda sensor?

If so and it is the splice-in universal type the performance can be varied given that they are made to be a Jack-of-all-cars type of thing and a master of none. It is not unknown for them to fail the emissions test even when newly fitted so fitting them can often be a false economy. Best really to buy one of known brand and reasonable quality with a plug fitted to it. Plenty on ebay such as Bosch for less than £45 and Lucas for less than £40.

JefferiesFarnol · 12th August 2021, 17:29

Quote:

Originally Posted by WillyHeckaslike

The missing part regards the circled bolt hole is a heat shield. It might have been deleted by Rover 2001 as part of project drive but not certain. Regards the map sensor, not sure why they would touch it and what the problem would be given that all 4 wires are colour coded and any splice should be connected like-for-like. Maybe they mean the Lambda sensor?

If so and it is the splice-in universal type the performance can be varied given that they are made to be a Jack-of-all-cars type of thing and a master of none. It is not unknown for them to fail the emissions test even when newly fitted so fitting them can often be a false economy. Best really to buy one of known brand and reasonable quality with a plug fitted to it. Plenty on ebay such as Bosch for less than £45 and Lucas for less than £40.

I thought it might have been some kind of heat shield since it was right above the exhaust manifold - thanks for clearing that up!

It seemed a bit odd that it would be the MAP sensor since, as you say, there are only four wires. I've just checked the invoice again and they did indeed replace the 'O2 sensors front and back' so I think you are right! Evidently the front one is below the manifold and the back is on the CAT, would I need to replace both of them, do you think?

Thanks for your help!

JefferiesFarnol · 12th August 2021, 17:30

Quote:

Originally Posted by Yorkshire GOC

And welcome to the fold by the way

Thanks!

11th August 2021, 18:32	#1
JefferiesFarnol Avid contributor Rover 75 Tourer Join Date: Aug 2021 Location: Canterbury Posts: 166 Thanks: 64 Thanked 18 Times in 15 Posts	MAP Sensor Wiring Advice Hello chaps, I have a question since I got my new 75 Tourer 1.8 back (at last) from its first MOT after being stored in a garage by the previous owner since 2016. The only major thing that needed doing was a new catalytic converter but I wasn't overly satisfied by the garage I took it to since they kept it for two weeks and when I needed to collect it, they said that an engine light was staying on because they replaced the MAP sensor. Apparently it already had an after-market one which was spliced to the existing cables and so they did the same. They said that the problem was that the wires weren't matched properly and they couldn't get it right without a wiring diagram but then said they could 'order a sensor with the plug' so that it wouldn't need to be spliced which would cost about £100. You might gather from that they aren't the best garage in the world. I left saying that I would take it back at some point for that to be done but I think it's the sort of thing I could do myself. I've really no experience with cars but I am a 'dab hand' at most practical things. It seems to me that the plug that attaches to the MAP sensor is part of the wiring loom and so you'd have to change that in its entirety to avoid any splicing. I suppose the other alternative is to splice it properly. I've attached some pictures and any advice will be much appreciated. (As a side note, is anything supposed to be attached to the circled bracket in the third picture?) Last edited by JefferiesFarnol; 11th August 2021 at 18:46..

11th August 2021, 18:53	#2
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	I cannot give you an answer but all MGR 75/ZT wiring diagrams are on the MGR RAVE disc which may help you or your garage. https://www.ebay.co.uk/itm/263709186...QaAlHtEALw_wcB __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.

11th August 2021, 19:38	#3
Yorkshire GOC I really should get out more....... Rover 75 connoisseur se v6 auto Join Date: May 2014 Location: Hull Posts: 2,069 Thanks: 1,842 Thanked 623 Times in 469 Posts	And welcome to the fold by the way __________________ She came off the Longbridge Line on 20-05-2003 The Silver Machine was the 13th of 160 Rover 75's to come off the production line that day and is the 100th of 527 Starlight Silver Rover 75 2.5 V6 Connoisseur SE Auto saloons listed in the build records produced world wide.

12th August 2021, 05:08	#4
WillyHeckaslike This is my second home Rovers 75 & 25 Join Date: Oct 2010 Location: Wearside Posts: 4,526 Thanks: 543 Thanked 709 Times in 511 Posts	The missing part regards the circled bolt hole is a heat shield. It might have been deleted by Rover 2001 as part of project drive but not certain. Regards the map sensor, not sure why they would touch it and what the problem would be given that all 4 wires are colour coded and any splice should be connected like-for-like. Maybe they mean the Lambda sensor? If so and it is the splice-in universal type the performance can be varied given that they are made to be a Jack-of-all-cars type of thing and a master of none. It is not unknown for them to fail the emissions test even when newly fitted so fitting them can often be a false economy. Best really to buy one of known brand and reasonable quality with a plug fitted to it. Plenty on ebay such as Bosch for less than £45 and Lucas for less than £40.