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1995-2002 Range Rover P38A
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Discussion Starter #1
I picked up a 2000 Range Rover HSE 4.6 this weekend as a project. It has some issues and has been sitting for a year or two, I have experience reviving old BMWs so hopefully some of that patience I developed working through those problems will carry over.

So first things first, I started down the electrical troubleshooting guide and took some measurements. Here is what I found:

Measurements

1. Engine off, all accessories on for 30 seconds, then off. What voltage

12.55



2. Voltage across battery at idle (no electrical load)

13.60



3. Voltage across battery at 2000rpm (no electrical load)

13.75



4. Voltage across battery at 2000rpm (everything electrical switched on)

13.82



5. Voltage at ALTERNATOR at 2000rpm (everything switched on)

14.02, I might have measured this wrong since I did what is described in #11


6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm (millivolts please)

91 mv



7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load

89 mv



8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle
9. Check voltage drop from 1st ground point to block
10. Check voltage drop from Alternator Housing to block

I was not able to get these done at 2000 RPM since my helper had to leave. I'll update with them tomorrow.


11. Voltage from alternator positive to alternator housing

14.02



What are your symptoms

The most immediate and troubling symptom is that when you try to accelerate when the truck should shift into 2nd it will instead display Gear fault and enter limp mode in some higher gear. Then when you have to stop at a traffic light it is very hard to get moving again.

Other indicators on are:


  • SRS Airbag light is on
  • Check Engine Light is on
  • Gearbox Failure
  • Traction Failure
  • ABS Failure
  • Occasionally the Bonnet open message will appear when it is closed

I have a Foxwell scan tool with the Land Rover code pack that I used to scan and rest the codes. I think all these Chinese scanners are basically using the same software in the end, but the messages don't always match with what one traditionally see.The code I have are:

DME:


  • 1f Rough road signal implausable
  • 60 Purge canister vent valve/DTML power stage fault

SRS:


  • 28 Front impact sensors configuration fault

ABS:


  • Front Right sensor output too low
  • Front Left sensor output too low
  • Front Right sensor output intermittent
  • Front Left sensor output intermittent

Transmission: No Faults

I am able to see the transmission and pull data from it fine. I was also able to reset the adaptations in case that would help. No luck there.

At this point I don't know if I should invest in a better scanner or not. The things I see online seem to indicate that their support of this vehicle won't be much different.



What have you done to fix it so far

At this point I have put in a new battery since the old one was clearly weak. I suspect that sitting over the Minnesota winter spelled its doom. I have also reset the adaptations and cleared the codes to see what would come back.

I am a bit confused about the numbers I have above, I read the fact that I only have 13.75 volts at the battery with no load at 2k rpm to be a sign of poor health. The fact that the alternator is putting out 14.02 volts, is low I guess, but I was not clear what I should be expecting in that measurement.

The voltage drops between the battery and the alternator directly being only 91 and 89 millivolts is under the 120mv threshold so I suspect that the cables and earth connections are good to go.

So what should I do next?


Is the alternator clearly toast? Can I expect all the issues this "ran when parked" truck are showing to be cleared up with just and alternator? Am I on the right path before I spend hundreds of dollars on a new alternator?
 

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Clean or renew the main power cables to the battery. The combination of volt drop over both negative and positive is what is giving the difference between voltage at the alternator and voltage at the battery. Low battery voltage will also almost always show up first with a gearbox fault as the gearbox ECU is seeing insufficient voltage. That may be all that is needed to clear the gearbox problem. Does the LED next to the gearchange and the gear display on the dash match with what gear you have selected? The ABS and TC faults are likely to just need the front sensors tapping back into place.
 

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1995-2002 Range Rover P38A
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Why buy a new alternator, check the windings and replace the brushes, $5.
you need the correct voltage before you try diagnostics I doubt very much if the Chinese scanner will read faults, it’s a dealer visit or one of the few scanners that are made for p38s, but there not cheap.
get that sorted first and see what happens
 

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1995-2002 Range Rover P38A
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Discussion Starter #4
Thanks, I will pick up a new set of battery cables this evening and give that a try, the set it has now have been replaced at some point in the past, the fasteners on them are SAE and not metric.

I can totally replace the brushes in the alternator and polish up any oxidation but is that enough? Does the rectifier need to be looked at as well?

The ABS sensor thing is interesting, do that work themselves loose over time? Is there a howto for tapping them back into place, or is it just as easy as it sounds?

Thanks for all the help!
 

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The Bosch alternators last really well, at least mine is original. I've got a set of bearings for it, hopefully I will rebuild it before it dies someday. I went through the same decision last year and ended up replacing the battery and cables and kept an eye on the charging system for the next month. Alternator maintained the new battery charge with no problem. Old cable look fine, until you take them off and realize how bad they are. I had my local Interstate Battery location build me a nice set of replacement cables, not sure if they do this nationwide. They had the heavy gauge wire and the extra lug mid-wire for grounding to the body. I replaced mine and I swear, my starter spun faster after replacement. Anyway, if you have the original one there or some crappy replacement, I would replace with quality new ones.
 

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1995-2002 Range Rover P38A
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Discussion Starter #6
I replaced the cable from the battery to the alternator and cleaned the grounding points on the block and the post that connects the negative battery cable and the block cable. I have a new negative cable on order, the one available locally was not a good option.

At this point is still has not fixed things, but I will keep the faith until I get that other cable installed.

I tried to better seat the front ABS sensors and did not get any improvement there. I could rotate them a little so I know they are not seized, but I saw no improvement there. I assume that the ABS system can be diagnosed in parallel while I am waiting on the new cable? I'll go home tonight and measure more voltages, what should I be seeing directly on the alternator going from the alternator's positive post to the alternator's case?
 

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The regulator in the alternator is normally the problem, so brush replacement sorts out any problems there, I’d be tempted to start going through the connections that give problems, each footwell has them, if there’s been any moisture they normally go green, I had one that as I touched it the lot broke away from the plug ( was fun )
it wont be anything drastic, these cars like keeping us on our toes
 

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Discussion Starter #8
So I have replaced the cables in the alternator battery circuit and these are my new voltages.

Across battery when off: 12.43 v
At idle : 14.22
At 2000 rpm full load: 14.23

At alternator at 2000 rpm: 14.28

Battery to alternator path at 2000 rpm
Positive: 69mv
Negative: 60mv

So, I think I’ll pick up a reman alternator and see if that is my problem. The battery is only a week old and so i assume that the charging circuit is still not up to snuff.

The transmission is still failing on the first shift.
 

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12.4 is low. A fully charged battery, at rest (nothing in or out) should be about 12.7
Your operating voltages look within reason to me. Possibly have the battery tested before tossing a new alt at it. I know, it is "New" but it could still be weak. If you are seeing 14.2 in the system, while running, and still have gearbox fault, the problem is elsewhere, not in the charging system.
How's the fusebox? the issues that an elderly fusebox will toss up are many! and yours would be consistent with a bad positive connection(s) to the fusebox, Becm (bottom of fusebox, and side of becm), or a toasted fusebox itself.
 

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Discussion Starter #10
I started looking at the fusebox and pulled a bunch of the relays, a few were corroded a bit, nothing atrocious but they could stand a little attention from some emery cloth on the terminals. One fan relay in the lower corner was sitting on some obviously melted and crazed plastic. Is that enough of a description to know if I should replace it. I looked at the thread on rebuilding one and it looked... daunting.

All the relays are black plastic and the one in the fan position is obviously a different brand. So, I expect that they have all been swapped out before.

Is this the obvious next candidate for a fix?

Thanks!
 

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The fact they are black is an indication that someone has suspected them in the past. Not a problem being black, BTW.
The fact that the fuse box is showing signs of corrosion and heat damage, indicates that it is compromised, and would be a logical candidate for replacement.
Be sure to get the correct one as there are several to choose from.
Look at the number on yours and order same.
 

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I agree with Bolt this sounds like a fuse box issue but I would check voltage across all the fuses with a meter and then do the same for the fuses by the BECM.
 

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Discussion Starter #13
I am set to have the new fuse box delivered on Friday, so I will let you know how that goes. I will certainly check the fuses by the BECM. I am used to testing continuity to see if the fuze was blown. But are you asking me to check the voltage to ground? I just want to make sure I am measuring the right things.
 

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Well given that the new fuse box is already on the way I'd go that route. It's an easy swap.
 

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Discussion Starter #15
I swapped the fuse box and no joy. Still have all the same symptoms.

I did notice that the computer for the transmission is reporting 14v and the computer for the engine is reporting 12v. I suspect I still have some voltage drop issues. I know about the ground for the BeCM but are there other things I should be looking at?

DHL just told me they left my new Nanocom on the door step so that might also provide some information... I'll let you know what it says.
 

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Discussion Starter #16
So, I committed the sin of splitting this off into another thread related to the Nanocom, I will try to continue this here. I have found lots of threads where people have an interesting problem and there is no description of what eventually happened.

At present I am getting a code that suggests a problem with the output shaft speed sensor, and looking at the live data form the Nanocom I am just getting a speed of 0. I thought that I had a wiring problem since there was also a 0 entry for the turbine speed sensor. However, I found out that the p38 does not use that input and has no turbine sensor.

I am working through the diagnostic flowchart and an at the step where it says to measure the resistance across the sensor at the transmission computer. I am getting a value of about 360 Ohms, the manual says I should be seeing about 1050 Ohms. I suspect that a wiring break would result in a higher resistance, so I am betting on a bad sensor.

I ordered one that should come on Friday, I ordered it under the BMW part number rather than the Rover number, since the only places I found the Rover branded part had 1-2 week lead times. It has the same ZF part number in the end so I hop that works out.

The only other bummer is that I just changed the transmission filter to see if that would help. I get to drain that thing again and listen to my sweet bride complain about the ATF smell in the garage.
 

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Discussion Starter #17
I got me sensor yesterday, I measured the resistance on the new sensor and it was in the 350 Ohm range, not the 1050 Ohm range described in the shop manual. Basically it is coming in at 1/3 the expected resistance, but that is also the resistance that I have seen noted as correct for a speed sensor.

I really don't know how to test this particular sensor beyond that. It only has two contacts so I don't think it is a hall sensor, I plan to swap it out tonight or tomorrow, but I would like to know if it is good before putting it in and be able to verify that the bad one was bad coming out.

One last thing, this is a new Rover sensor, not the BMW one I was talking about getting. The BMW guys said that the warehouse had one but it never shipped so I canceled and had this sent over the pond.
 
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