Cruise control...gurus? Need help

9730 Views 37 Replies 5 Participants Last post by slvdc1, Aug 24, 2009

slvdc1

Discussion Starter · Jul 22, 2009

Hi all,

Been about 2 months since I got my rangie, been fixing little things here and there (tightened up the steering box, replaced some bulbs in the switches, had to disassemble some of the switches as they were not functioning/corroded, fixed gunked up air inlet valve, fixed seat switches, replaced fog lights, got the eas system all repaired and rebuilt so that works now...most of the time)

Anyway back to the current issue, cruise control. i swore to myself I should be able to fix this thing but I am out of ideas.

Firstly I took the cruise main switch apart and cleaned it all up b/c it wasn't turning on. So now the cruise master switch turns it all on good right? nope still wont 'set'.
Then I tested the vacuum diaphragm, holds vacuum just fine (no leaks)
Next I got my hands on a replacement cruise computer from a 93 range rover and tried that...nope
Then I got a replacement vacuum pump...nope (actually bench tested my current one, works fine)
Then I took the vacuum release valve/switch off and checked it, switch was good, valve was good
Lastly I applied vacuum to the lines from the vacuum pump and watched the diaphragm valve compress like it should and hold, so no leaks at all in the system.

At this point all the components check out so I was at a loss. I stumbled upon the 15pin cruise computer pin-out so I decided to check all of these
The set and res switches were fine
the comp was getting power
then i went to measure the 12V for the brake switch WITHOUT the peddle pressed....I got 0V...hmm. So I pressed the pedal and saw 12V so THIS IS BACKWARDS? its supposed to supply 12V to the system then drop to 0 when the pedal is pressed but its the opposite??!???!

So if anyone can shed some light on this I would be forever indebted to you :-D

Shane

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1 - 20 of 38 Posts

Rich998a

· #2 · Jul 22, 2009

If you look in RAVE at the ETM section for the Classic, B5 within the 'Circuit' section outlines tests you can do using a multimeter. It's a similar set up to the early V8 p38's.

slvdc1

Discussion Starter · #3 · Jul 22, 2009

OK. I will go through and check those. I didnt think the vacuum pump was on the whole time ie: only when you hit 'set' so I didnt bother to find out for sure if its running.

slvdc1

Discussion Starter · #4 · Jul 22, 2009

AHA! I think my brake switch is working properly. If I understand the paragraph correctly if its in P or N there is another solenoid which will int interrupt the switch or reverse the function of the switch. So my gut tells me I may just have an open circuit somewhere (harness that powers the vacuum pump?) I will test for 12V at the pump connector while its running with the cruise switch turned on

Shane

classicjack

· #5 · Jul 23, 2009

This all sounds very familiar. I've been troubleshooting my cruise control for about a year with all the same results as you, I recently started driving with out steering wheel center piece which covers connector to spiral cassette ( also replaced recently from parts car ) and found these four wires when jiggled allow cruise to work. Loose wires at ecu and at this connector finally allow cruise to work, has been working now consistently for a week, for the first time in a year.

slvdc1

Discussion Starter · #6 · Aug 7, 2009

classicjack said:
This all sounds very familiar. I've been troubleshooting my cruise control for about a year with all the same results as you, I recently started driving with out steering wheel center piece which covers connector to spiral cassette ( also replaced recently from parts car ) and found these four wires when jiggled allow cruise to work. Loose wires at ecu and at this connector finally allow cruise to work, has been working now consistently for a week, for the first time in a year.

Difficult for me to remove the steering wheel...with the airbag and such...plus I already tested the wiring for those two switches and they check out fine. I pulled the brake switch/valve apart tonight and found nothing worth noting, the switch is fine. I have come so suspect something else though...its called the"cruise control lockout relay" What it's supposed to do is shutdown the cruise control computer when its in P or N. If this relay is bad that would explain everything...only problem is I have no clue how to find it LOL.

Kind of a side question...the bracket that is attached to the accelerator bracket on the throttle body has about 1/2" or free room before it would begin to open the throttle...is that normal? I don't see any way to adjust its pos...just thinking out loud here....

I will pull all the relays I can find behind the glove box that match the diagram for the "lockout relay" tomorrow and bench test them (crosses fingers)

Still have not checked for power at the vacuum pump b/c that harness is quite short I can barely get a finger on it to unplug it. Will try to figure something out here

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slvdc1

Discussion Starter · #7 · Aug 7, 2009

One more quick question...is there an indicator in the instrument cluster that indicates that the cruise is operating or is the main switch the only light?

adam1977

· #8 · Aug 7, 2009

I've had similar problems since owning mine, I've been through the RAVE diagnostics, everything clicks when I set the cruise etc. :think:

The next thing I'm going to do is rig up a test light on the vacuum pump itself, with the bulb sticking out of the bonnet between the decker panel (so I can make a visual reference) If there is power to it then I have a weak pump, maybe this method will help you too :think:

P.S: I believe the light on the cruise switch is the only indicator.

slvdc1

Discussion Starter · #9 · Aug 7, 2009

adam1977 said:
P.S: I believe the light on the cruise switch is the only indicator.

AH I was wondering this because there is a lamp in my instrument cluster that is next to the "TC" lamp that looks like an overhead view of the drive train showing the 4 wheels, axles, and drive shaft in the pattern of an "H" ...must be for something else then :think:

adam1977

· #10 · Aug 7, 2009

I wonder if that's a 'diff lock' warning lamp :think:

slvdc1

Discussion Starter · #11 · Aug 7, 2009

Could very well be..never locked mine haha. we'll see it in the snow this winter I bet. Hopefully after lunch today ill get some free time to look into the relays.

Anyone have any idea which relay is the "cruise control lockout relay"?

slvdc1

Discussion Starter · #12 · Aug 7, 2009

UGH I pulled all the relays that match the function (they have the pins: 85, 86, 87, 87a, and 30) and bench tested them all and found no problematic ones :x

The rave manual says the lockout relay is located in the passenger footwell, is this the area behind the glove box?

adam1977

· #13 · Aug 7, 2009

It is on the passenger side if yours is a right hand drive example...which it isn't :think: so maybe it's behind the drivers side?

i can't remember how I figured out which relay was the lockout one, I might have followed the RAVE instructions and felt the correct relay when it 'clicked' :think:

slvdc1

Discussion Starter · #14 · Aug 7, 2009

adam1977 said:
It is on the passenger side if yours is a right hand drive example...which it isn't :think: so maybe it's behind the drivers side?

i can't remember how I figured out which relay was the lockout one, I might have followed the RAVE instructions and felt the correct relay when it 'clicked' :think:

I suppose if I had a helper to turn the main cruise switch on and off i could feel around. But looking at the rave manual its a normally closed relay that opens when its in park or neutral. So I was wondering how likely this could be the problem since if its failed then it would just not open right?

adam1977

· #15 · Aug 8, 2009

I've just been refreshing my memory with the cruise control troubleshooting guide, the CC lockout relay is located on a metal carrier that hinges down once a nut is loosened and taken out on the passenger side of a right hand drive car. As I've never worked on a LHD Rangie I can only presume that yours is on the passenger side too (I'd have thought it would be too cramped to put all this where the steering column goes).

The metal carrier also holds the alarm ECU so can be easily identified; once you've located it then look for the 5 terminal relay that has the same white/slate wires as in the trouble shooting guide (page 15-terminals 86 & 30) follow the procedure as stated in the guide (test 4B) and if it passes the test move on to the next one (test 5B).

According to the guide, if it has failed then the causes are: WS wire, WY wire or the cruise control diode.

Let us know how you get on; all of this is making me want to re-investigate my own non functioning cruise control

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slvdc1

Discussion Starter · #16 · Aug 8, 2009

adam1977 said:
I've just been refreshing my memory with the cruise control troubleshooting guide, the CC lockout relay is located on a metal carrier that hinges down once a nut is loosened and taken out on the passenger side of a right hand drive car. As I've never worked on a LHD Rangie I can only presume that yours is on the passenger side too (I'd have thought it would be too cramped to put all this where the steering column goes).

The metal carrier also holds the alarm ECU so can be easily identified; once you've located it then look for the 5 terminal relay that has the same white/slate wires as in the trouble shooting guide (page 15-terminals 86 & 30) follow the procedure as stated in the guide (test 4B) and if it passes the test move on to the next one (test 5B).

According to the guide, if it has failed then the causes are: WS wire, WY wire or the cruise control diode.

Let us know how you get on; all of this is making me want to re-investigate my own non functioning cruise control

So this is below the glove box it seems. I will investigate the correct relay and report back....though its raining right now so iI wont be able to for a little while.

Currently building myself a box to manually select extended profile....where its nice and dry inside

slvdc1

Discussion Starter · #17 · Aug 8, 2009

UPDATE: I decided to take the laptop into the rangie and run through the test procedures. Before I did that I located the lockout relay down in the passenger footwell...it was fine.

So starting at test 1A PASS
2A FAIL goto 3A
3A FAIL

So it says its one of two things: either the brake switch vent valve, OR the PG (pink/green?) wire

So testing the switch itself it opens and closes correctly indicating that the switch is indeed functioning...so the problem is there is no 12V being fed to the switch in the first place. Does anyone have any idea where to go next? The rave manual just says the "problem cause : PG wire" with no solutions listed LOLOLOL :roll:

I will try to trace those two wires to see where they come from though I don't know how far I will get.

Many thanks thus far guys

Shane

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adam1977

· #18 · Aug 9, 2009

You need to do Test B; Test A is for manual gearbox cars only. Start with Test 1B and work through the procedure

slvdc1

Discussion Starter · #19 · Aug 9, 2009

adam1977 said:
You need to do Test B; Test A is for manual gearbox cars only. Start with Test 1B and work through the procedure

AHA! Well that makes sense...though I dont think it makes a difference because there is still no 12V to that switch at all :doh: I will however look at Test 1B as soon as it cools down outside.

The purpose (as I understand) for the 12V from that switch is to supply 12V to the cruise ECU and then when you apply the brakes it cuts the 12V AND releases any vacuum in the system correct? I dont know where that 12V is supposed to come from...I traced that wire up into the dash but cannot see where it ends

slvdc1

Discussion Starter · #20 · Aug 9, 2009

OK. TEST B results:

1B: pass
2B: fail
3B: fail
4B: pass
5B: here I tested the resistance of the different positions of the gear selector. I SHOULD have gotten 0 - 1 ohms in park and neutral..... RESULT: in park I got 22 ohms and in neutral I got an open circuit (inf resistance)

As for the rest of the selector positions they should have been > 100 ohms and they were very high resistance (O.L on my meter)

So what does this mean then? Either the BY or the BO wire is bad OR the gear selector switch is bad.

I think at this point I should pull the surround off the gear selector and see if I can find the switch and test it directly and its wiring/connector

Any other ideas?

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