P38 Cruise Control woes

[Romulus]

Ok, its time to get serious about and see if I can't get it going, the cruise control on my P38.
Now, I have replaced EVERY part of the cruise control circuit, checked the vacuum hose and it is still not working, any ideas?
I can hear the relay coming in when I push the steering wheel buttons but for some reason it just will not engage.
Is there a way to test it whilst in my drive way with the bonnet up?, thanks for any help.

[andrew e]

check that the pedal switch is adjusted properly?

[Scouse]

I'm going through similar problems with mine - 10% of the time it works but the rest it doesn't.
It started off not holding speed & a new pump fixed that straight away for a few months. Now it's just intermittent :(.

Have you gone through the LR test procedure?
I went through the whole lot & it passed everything so it's pointing to the CC ECU. Next drive, the cruise worked :mad:. An hour later, it didn't.

My test voltage readings are withing spec (I believe) but I think they're too low (11.5v) so I'm going to bypass the BECM power output & make sure the system is getting full battery voltage.

[PaulP38a]

Tend to agree with Scouse... I had exactly the same problem with the Cruise Control in my previous '95 HSE... I could hear/feel it trying to engage but it would not most of the time - replaced the Cruise Control ECU and it came good again.

[Romulus]

I have already replaced everything, the pump, bellows, brake pedal switch, ECU, relay, checked the hose.....nothing left to replace :-).....

[Scouse]

I have already replaced everything, the pump, bellows, brake pedal switch, ECU, relay, checked the hose.....nothing left to replace :-).....Ahh, so you've followed the backyarder test procedure :wasntme:.

The cruise system gets it's power through the BECM. If there's a problem there, then nothing will work.

Do you want a copy of the test procedure? It's quite easy to follow if you have a multimeter. PM me an email address if so.

[Romulus]

Ahh, so you've followed the backyarder test procedure :wasntme:.

The cruise system gets it's power through the BECM. If there's a problem there, then nothing will work.

Do you want a copy of the test procedure? It's quite easy to follow if you have a multimeter. PM me an email address if so.

isn't that the only way to repair?? ;-)

yes, can you either pm me or describe it here, got a multi meter so no worries, thanks for that!

[adm333]

Scouse

I would love a copy of that as well if you don't mind.

Cheers
Dave

[willem]

Scouse

I would love a copy of that as well if you don't mind.

Cheers
Dave

That would be really useful, and I'd like a copy too! (You might as well post it up here!)

Thanks

Willem

[MoodyBlue]

Same as Willem.
My Brother in Laws 97 (He just bought it) CC does not work and I am about to help (or hinder) him in getting it going.

Cheers
Jeff

[andrew e]

That would be really useful, and I'd like a copy too! (You might as well post it up here!)

Thanks

Willem

Just to let you know Willem, The bosch/mid 99 and onwards p38s like yours had a different cruise ecu. The diaphram, pump and all the other parts thet bugger up are the same.

Andy

[Aussie]

I just replaced the small plastic T piece and the 2 smaller hoses that run of it. They had cracked.

[Romulus]

well I've given up trying to fix mine, checked all hoses, modules etc., could not find the problem, so I removed all cruise control components and installed an after market unit, now works like a dream :)
Sure, I can't use the steering wheel control, but the after market unit is a neat little control panel which I mounted on the drivers side wood trim under the vent, almost looks like it is meant to be there :)

[Scouse]

So I should keep an eye open for a cruise control ECU on eBay?
:):)

[Romulus]

So I should keep an eye open for a cruise control ECU on eBay?
:):)


hehehehe...ya never know!!;)