Cruise control - Range Rover







From: Jeffrey S Johnson <>
Subject: [RR] Cruise control repair

I think I finally nailed the problem with my cruise control, I took the
board out before and re soldered the plug pins but that didn't get it.
It has been working on and off but was getting harder to set, I'd checked
all the inputs and they looked okay so I figured it was a board problem.
Today I took the board out again and stripped off the lacquer on the back
with fingernail polish remover and re soldered every solder joint on the
board.  Put it back in and it's worked fine everytime during a long test
drive, as it was I may get it to set once but then it wouldn't work again
for several days.

For automatic trans you can check the pin outs with a DC volt meter to
ground for the negative lead, ignition on, unplug the 15 pin plug to the
CC ECU.   Pin #10 should have power with CC main switch on, if not check
fuse.  Auto in drive, switch CC main switch on Pin #9 should have power
and drop out with brake pedal pressed way down or trans set to N or P, if
no voltage on #9 check brake switch or trans lockout relay. 

Ignition on and CC on, check pin #3 press "set/ Accel" power should be on
#3 with switch operation.  Check pin #5 power should be on and go off
when brake pedal pressed.   Pin #4 push "RES/DECEL" power should go on
and off with switch.  Pin #11 should show fluctuation in voltage between
0-12 volts when right rear wheel down on ground and left rear wheel
jacked up and turned by hand. Pin #5 is from stop lamp switch and #9 is
from the vent valve switch, I found the vent valve switch needed the
brake pedal pressed quite far since the vacuum valve is first to trip in
that switch, the vent valve switch to pin #9 seems to be a back up safety
cut off.

For jumpers I cut small blades from brass stock and soldered wire to them
so I could plug them into the 15 pin plug hands free.  Install jumper
from pin #1 and #10 on the 15 pin plug and another from #7 to ground and
the CC vac pump should run, remove jumpers.  Install jumpers from pin #1
to #10 and another between #6 and #7 and ground, actuator on throttle
should retract, if not but the pump runs check the vac lines as well as
the solenoid coil in the vac pump unit which operates the valve. 

This list is to help locate the problem and check the switches on the
steering wheel.  If you compare these pin outs to the schematic in the
owners manual you can see what they do as inputs and outputs to the ECU.
I had already repaired the hoses and all these tests checked out okay so
my last effort was to repair or replace the ECU.  I decided to try and re
solder the board before trying another ECU and the solder job fixed the
problem.  I'll probably reseal the back of the board with clear
fingernail polish just so it won't be effected by moisture.   Manual
trans is much the same but they have an engine speed relay that drops out
at 5k rpm as well as a switch on the clutch and I think one on the trans
for neutral position.

I received a few e-mails off list requesting the pin outs for the 15 ECU
plug after I mentioned I had that list but it's on a CD and there's no
way I can copy and paste the info to a file so this is the best I could
do.  Hope it helps and if there are questions feel free to ask on or off
list.  This is on a 95 Classic Hella ECU type cruise control but I
believe they used the same ECU for many years in the classics.

95 RRC
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