97 Passat Cruise Control Doesn't Work

Can someone tell me how to diagnois the problem and what to do to fix it? Is there a thread on here that describes the process similar to the the ones that tell how to change a timing belt? Don't currenlty have a Vagcom.

Thanks

Heyya fellow Michagander!

You are going to need a vag-com to do this. The cruse in your TDI is totally electronic... the only mechanical parts in the system are the cruse on / off switch, the brake light switch, and the clutch switch. With vag-com you can view the status of these switches and see which one is kaputt.

You don't have burnt out brake lights, do you?

-Jason

Try setting it with your left foot under the clutch pedal and pulling up. The clutch switch has been the culprit when mine have failed. The switch moved up in its mount and wasn't being closed by the pedal arm. Repositioning the switch and securing it fixed my problem on two B4s.

Burnt out brake light can do this. The computer uses the brake circuit to detect when brakes are applied. If the bulb is missing or dead, the computer 'thinks' you foot is applied and will not engage the cruise.

Nice to see another Michigander in the club.

I did notice this afternoon that both brake lights are working however, the one on the right is significantly dimmer than the one of the left. If the light has multiple filaments and 1 is broken could that be the culprit?

I've got a vagcom on order. Hoping it will be here be the end of the week.

Lug, could the clutch switch also be a cause of intermittent resuming? I have been living with this idiosyncrasy of my Passat with various degrees of dignity for years...

The clutch switch or brake switch move up on my list of potential culprits if the intermittant cruise drops out after running over an expansion joint in the road.
I also believe (It's been a while since I looked) that the brake pedal arm has two switches. One, contacts normally closed and held open when the pedal is up, operates the brake lamps. The other, normally open and held closed when the pedal is up, maintains the cruise.
In other words, brake light operation has nothing to do with cruise operation. These are two different switches, one opens to cut power, the other closes to supply power.

Edit- never mind!

Jeff, no vacuum involved in the TDI cruise control. Drive by wire allows it all to be done in the computer.

A 97 B4 TDI has drive by wire? I thought B4 TDI's had cable throttle.
I wish my car had a sophisticated CC system like that.

Nope, all TDI's are DBW.

DBW is what makes the TDI possible... the injection pump is comptuer controlled, and that's what makes it so much more refined then the previous diesels, and have fewer emmissions.

-Jason

The Canadian 1995 B4 diesel came with an AAZ code engine(peak 75 hp at 4200 rpm, 110 torque from 2400 to 3400 rpm). This engine has a cable operated fuel pump, no ECU, no intercooler, a driver's door initiated engine glow timer, and a cold start enricher cable. This engine is directly injected and turbocharged, but not marketed as a "TDI".

I thought the AAZ's had prechamberes

-J

jck66 said:

Nope, all TDI's are DBW.

Click to expand...

Thanks for puttin' up with the newbie.

Problem fixed!

Lug_Nut said:

Try setting it with your left foot under the clutch pedal and pulling up. The clutch switch has been the culprit when mine have failed. The switch moved up in its mount and wasn't being closed by the pedal arm. Repositioning the switch and securing it fixed my problem on two B4s.

Click to expand...

Bingo! this was the problem, with a minor repositioning of the switch, it's as good as new. I wont miss setting the cruise by lifting up the clutch peddle only to have it stop working at the next expansion joint down the road.

Thanks for sharing your experience and tips!

I must post here mentioning I had the same problem with my B4... I had the clutch switch moved somehow when my mechanic replaced the clutch fork (it broke in there... how.. noone knows). Investigation with VAG-COM showed that the ECU was seeing the clutch pressed when it wasn't.

Fixed by minor repositioning