Cannot connect to OBD port

[Borgy]

Mechanic tried to connect to the OBDii port but his faultmate computer says unreadable and cannot connect.. tried 2 different scanners but no luck on both..
Cleaned out the female end of the contacts.. but still unreadable.
No issues with the vehicle ..it's just the ABS and TC light come on after a few stops.
Have changed the accumulator, new alternator, new battery..
Did notice the lights on the hevac screen stopped working roughly 2 weeks prior to the other issue.
Not sure if it's a grounding issue or what..
Fuse box was changed out when I 1st got the vehicle.
Anyone else have trouble connecting to the OBD port to diagnose issues..?

[p38arover]

Some cars have had corrosion issues with the connector. Drop the panel and have a look from the back of the socket.

Labtronx in Mittagong do a replacement for them:

Data Connector (https://www.labtronx.com.au/labtronx-products/data-connector/)

Changing the globes in the HEVAC panel is relatively easy. Unfortunately, my write up on how to do it has, along with all the other servicing articles, has been deleted from RangeRovers.net.

[p38arover]

Found it on the Wayback Machine: LCD Backlight Repair (http://rrnet.gadsdenrovers.com/repairdetails/lcdlights.html)

[Tins]

Found it on the Wayback Machine: LCD Backlight Repair (http://rrnet.gadsdenrovers.com/repairdetails/lcdlights.html)

Stick it in TGO, Ron. That way it won't get lost again.

[Borgy]

Excellent ..that'll make it easier..
Thanks

[p38arover]

Further to the comment about corrosion, here's what Labtronx say:


Check the diagnostic socket in your vehicle for any signs of moisture or corrosion. Use a mirror and torch (flashlight) to illuminate the socket and visually inspect it. If there are any signs of water or corrosion, please order and fit a Data replacement diagnostic connector.

[Borgy]

Tomorrow is the day for exploratory surgery..

Here's the only other hiccup I have on the p38....touch wood.
Starting vehicle and driving for 10 minutes, all is super smooth and comfortable, then the dreaded ABS light comes on then the TC light, then no brake pressure and no brakes. I turn it all off..lights dissapear after 2 or 3 tries, then again to the 3 lights come on after 5 or so minutes of driving..

1st time it happened I was driving down the hills in turrumura and NO BRAKES..2 dogs in the car and 20 minutes from home. No panic..drop down through gears, handbrake and stop. That was easy. So limped home that way. There was lots of brake fluid lost. Changed out accumalator, new alternator and battery, and problem still persists. But as mentioned can't read the faults..

Anyone experienced this?

[p38arover]

I did experience the brake problem a couple of times before I changed the pump and accumulator but the symptoms differed from yours.

I was at work and had to go and shift the P38A. I hopped in, drove forward, and had ineffective brakes and crashed into a row of wheelie bins (fortunately). The pump hadn't built up enough brake pressure. I had to leave running it for a short period to get pressure then it was OK. It happened a couple of times - eventually I was smart enough to wait before driving off. :)

[Scouse]

There was lots of brake fluid lost. Where was the brake fluid leaking?

My OBDII connector wouldn't connect to any diagnostic gear but the corrosion was at the RH A pillar connection block.

[Borgy]

The brake fluid was coming out of reservoir cap then dribbling down and over everything.. I'd guess about a litre or 2..but after the accumulator change over all went well for a few trips.. then the gremlins started.
I reckon the car got jealous because the loss of brakes happened just after I inspected and bought an svx defender.. 2 plus years and over 60k of driving without an issue..and then, within 30 minutes..!! Some strange X files, Stephen King going on here.

I'll check out the connection blocks at the A pillar.

Would be interesting to know how many metres or kilometres of wire are in a P38.

[Scouse]

If it's coming out of the cap that suggests that accumulator/pump pressure is leaking into the reservoir through the ABS modulator.
There's a lot of wiring but a lot less than there would be normally due to multiplexing.

[prelude]

I have the same issue.

Ever since I replaced my accumulator and revised the ABS modulator the pump runs more often and loses pressure more quickly. It seems to me that it is not the pump itself since I hooked up a pressure gauge to the pump output directly and let it run up to 160bar and left it for a few days without it dropping. When it's all connected up however the oil runs back into reservoir, suggesting to me that whatever "blocks" the pressure inside the modulator is leaking internally causing the excess to run back into the reservoir, it does not seem to be the pump.

Cheers,
-P

[Borgy]

Tried holding it down. Keeps the pressure at around 50mm pedal travel. But only when driving after a few minutes pedal drops.
Even read on rovernet about holding pedal depressed overnight and how that releases little air bubbles trapped in the lines.. did that for 3 days..but main issue is
I still can't connect to OBDii port. Tried to clean every connection I could find under both seats behind both kick panels. ABS module thing.
Checked for corrosion or green spots on all connectors.
Sprayed contact cleaner on everything. Tightened the connectors in the OBD port.
Nanocom powers up. Reads the airbag and EAS but error communications the the ECU..
It's not the nanocom as it reads everything with the puma. And it's the correct adaptor lead..
Stumped.!!

[prelude]

I am currently in the progress of completely replacing the BECM, if at all possible, with a homemade installation and for that I had to identify all connections to and from the BECM. I can share whatever info I got from this so perhaps this helps you?

From memory (I can't connect to the GIT repo containing all the data of this project from this PC right now) the data line that communicates with all the individual parts is shared amongst all components, including the BECM itself. The first go would be to clean all the connectors thoroughly which it seems you have done. Second would be to see if there is any data flowing. Do you have a scope at your disposal or one you might borrow? The data protocol can be seen easily with a fairly cheap scope.

I will try and dig into the docs to find the relevant pins. I do suspect however if in the end you can not connect to the ABS/TCS unit (that is one item) the problem might exists there. Although diagnostics communications are not part of the primary function of the unit, it might suggest that that module is defective.

The pinouts are in the RAVE manual if you have one, but I will look the, up this weekend just to be sure :)

Cheers,
-P

[prelude]

I have been going over my documentation and as it turns out, what I am looking for is not in there :(

To put this into context: This project is about replacing the BECM only so we have only documented the connections to and from the BECM itself. I can confirm that the ODBII protocol datalines do not connect to the ABS/TCS unit from the BECM, they must run directly (I think it is some sort of bus where they are all connected to the same pins on the ODB connector). It does occur to me that I do want to communicate with the devices that remain in the vehicle so I need to figure that one out myself as well but unfortunately I can't do that on the fly right now.

Suffice it to say that apart from a splice somewhere maybe cleaning the connectors at the ABS/TCS end and in de ODB connector should give you the desired result. Checking for a proper ground can be beneficial as well since that can cause erratic behaviour. When I get around to digging up the pins myself I'll post it down here, when needed.

-P

[prelude]

ABS computer PIN out and explination | Range Rovers Forum (https://www.rangerovers.net/threads/abs-computer-pin-out-and-explination.44972/post-372803)

Here you go :) pins 13,14,27 it seems need to have data going over them that is 13,14 are the diagnostic lines and 27 seems to be ground. The protocol is ISO9141 but suffice it to say that you should be able to see data on those buses with a scope.

Noteworthy is that the ECU will ONLY communicate when idle it seems, once the road speed has exceeded 2kph on any of the wheels it shuts down the diagnostics ports and dedicates all it's CPU power to doing it's actual job so perhaps there is a cause for the problem you have. Maybe the unit thinks it has moved? (incorrectly)

Cheers,
-P

[Borgy]

Thanks for that..
I've gone through a lot of the connections and cleaned all the pins. They're all solid and no rust yet it's still not reading.
When I first bought the vehicle the a.c drain rubber grommet was blocked and water backed up and dropped down and over the OBD ii port. But it ran fine for 2 years. I'm thinking I've missed maybe some connectors that are back up inside the dash.??
Maybe that's the next port of call.

The P38 is like a blind man walking through a crowded nudist beach. You just have to feel your way through it.

Great car except for this one hiccup.

[biggin]

Disconnect plug at ECU and check wiring for continuity and shorts between OBD plug and ECU plug. Don’t worry about what lies between unless you find a problem. Assuming you have a multimeter. [emoji106]