Hello veterans of the Land Rover ownership struggle. I have a 2004 Discovery with 116,000 miles that I've owned for about 2 months now. I bought it with no lights or any running issues, and drove it home from Chattanooga, TN to Tampa, FL with no problems. I bought an Ultragauge to monitor everything on that long first drive, and didn't have any problems.

But now I am having problems! Here are my symptoms: The first sign that something strange is going on is that my Ultragauge will flash and lose data intermittently. It never loses power from the OBDII port, because it doesn't have to rescan to see what protocol to read from, but the whole screen will just go blank for a few seconds. Then, I started getting a pending P0141 code for the Bank 1 Sensor 2 O2 sensor. The Ultragauge will also lose data at times. For example, when I was monitoring the live data from the O2 sensors, the Ultragauge would occasionally read ERR instead of a number. Now, I just started getting a misfire in cylinder 5, and my Ultragauge is missing a lot of sensor data. There is no coolant temperature reading, no O2 or fuel trim readings. Only things that the Ultragauge measures from itself, like gas mileage remaining. My fear is that the ECU is bad. My windshield cowl is all cracked, and we just had our first summer storm here in Florida last night, which is when the misfire started. Is there a chance water is pouring straight down into the ECU? I haven't noticed any water in the footwell, but the sunroofs were just starting to leak when I bought the truck. I've since resealed them and redone the headliner, and there are no signs that any water is getting in from there.

Since I've bought the truck, I've changed all the fluids except coolant, which I'll be doing soon since I just got Extinct's kit in the mail. The O2 sensors and wiring are new, per the PO, and per my inspection of them a couple of days ago. The spark plug wires are also new, per the PO. I don't know about the plugs themselves, or the coils. I was planning on doing the headgaskets in the next couple of months, and thinking about replacing the coils while I was at it due to their location.

My main question is, should I be concerned about the ECU, or some other part of the engine management system, or are these things unrelated to each other? Do I just have a misfire and an unrelated problem with the OBDII port?

 

I'm debugging a similar issue with my Ultragauge where it will sometimes just stop reading out and show Err. I saw on another thread that it could be a crankshaft position sensor (CKP) but I replaced mine and it didn't seem to solve the issue. I also had a slight miss which went away after changing my spark plugs but the Ultraguage error still exists. Ultragauge support was pretty lackluster when trying to debug so I'm not sure what to debug next on that front. I just unplug and reseat when it does Err and it begins working again.

 

Thanks andino. Unfortunately, my Ultragauge still won't read anything. I've unplugged and replugged it, and power cycled the truck a couple times to no avail. Also, I placed an order for the windshield cowl, or central air intake, as Atlantic British call it. $63 shipping hurts, but it needs replaced. I'll pull my spark plugs and see how they look.

*Edit* I just plugged in my standalone code reader, and it is also unable to communicate with the vehicle. So my OBDII port is dead.

 

The cowl plastic is more trim than barrier. if it leaks water goes into a metal trough and runs out at the ends assuming all is working correctly there. BUT if you have any cracks in the metal seams of the firewall or A pillars that would allow entry.

 

That's good to hear. Question: is the Slabs computer the same as the ECM that the RAVE manual talks about? I don't want to throw parts at this, especially not parts as expensive as this, but if I need to replace it, it is good to know that I can get a new one. I'm not really sure how to diagnose the issue with the OBDII port being dead. Can anyone tell me where to start?

 

First the SLABS (Self-Leveling Anti-lock Braking System) computer is not the same as the ECM (Engine Control Module). The DII uses several computer modules. In addition to those two there are the:

• BCU (Body Control Unit)
• Supplementary Restraint System (SRS) or airbag DCU (Diagnostic Control Unit)
• transmission ECU
• cruise control ECU
• and, if the truck is equipped with Active Cornering Enhancement there’s an ACE ECU.

The standard OBDII diagnostic socket has 16 pins, but according to the electrical circuits diagram, only four are active on a petrol DII. One is power, two are grounds, and ALL the data from all six or seven computers are on the fourth wire. If the UltraGauge powers on you have power and ground. Before jumping to the conclusion that you have a bad ECM, I’d check continuity on the pink wire that’s on Pin 7 of the diagnostic socket.

 

Excellent, thanks mln01! I'll get my multimeter out and see what I can find.

 

I would stick with your theory that moisture got in due to recent storms. if you google this it's not that uncommon due to water ingress under the dash. gets in a harness jacket and corrodes the connectors. I dont have the links right now but this forum has several addressing the same issue.

 

There's a big hole on the passenger side, under the windscreen cowl where the hvac pulls air in. Depending how bad the cowl is cracked and how bad the rain is, water easily gets in there and will drip through the ducts onto the floor, possibly getting to the control units against the pass side outer wall and anything else around.

 

Only things that the Ultragauge measures from itself, like gas mileage remaining

There is no means for the UG to measure your gas mileage, it just makes an estimate based on the miles driven and user input of fuel. So this is not a broken part of your system.