2003 S60 Drops out of cruise and goes into limp mode

maddog2020 · Post by **maddog2020** » 18 May 2014, 16:00

As the subject said, if I engage cruise it's fine until the car has to open the throttle to go up a hill in which case it always throws a U0073 and goes into limp mode. If I pull over, turn off the ignition and start up again, it's all fine.

Wondering what the likely cause is, seems like it almost has to be an ECU/TCU issue. Thoughts? Bast solution if it is ECU/TCU?

Ian

Post by **abscate** » 18 May 2014, 17:22

On electronic throttle body (ETB) cars if the module throws an ETS code the cruise will be disabled. Remember the cruise control is all electronic on these cars, it does not open the throttle by cable, it uses the ETM.

Post by **jimmy57** » 18 May 2014, 20:46

How are you reading the codes?

maddog2020 · Post by **maddog2020** » 19 May 2014, 09:50

It's not the dropping out of cruise that worries me, it's the motor going into limp mode "engine performance reduced" that is the main concern.

Unfortunately I only have a basic Autel Scan tool, so I can only see the ODB/II codes, not the Volvo specific codes.

Post by **abscate** » 20 May 2014, 05:00

We see very few ECU issues on these cars. Something else in the engine management system is amiss

maddog2020 · Post by **maddog2020** » 20 May 2014, 15:14

Did a bit more research and determined the following.

1 - it happens right at the point where it feels like the car wants to downshift from 5th to 4th
2 - it doesn't happen if I manually shift (cruise remains engaged)
3 - if I shift to 4th well in advance of the point at which it would shit itself then it doesn't happen

This seems to indicate that there's something wrong with the interaction between the ECM and the TCU, maybe a faulty TCU?

Ian

alron400 · Post by **alron400** » 23 May 2014, 05:10

Hi Guy's,

: The "ETB" is a poorly designed unit that wears badly" and it must be cleaned to allow it to work properly.

If you do the work then the results will surprise you, as I found out on my P2 Wagon.

Everything that you read about poorly work "ETB" is true and when you clean them up the perform great again.

: The Idle drops and the Car will run a lot smoother as well.

The Cruise should also work a lot better as well, see how you get on, I hope it helps.

Catch you on the Open Road.

maddog2020 · Post by **maddog2020** » 23 May 2014, 08:37

Probably all true, but my car doesn't have an ETM. 2003 (maybe 2002) and later models have an updated Throttle Body. That said I still think it might be my throttle body failing.

maddog2020 · Post by **maddog2020** » 31 May 2014, 12:14

Thanks to the suggestions of the knowledgable folks on this forum I seem to have got this fixed. I figured from the input from this group that it might be caused by one of 3 things:

1 - Turbo (Boost) Control Valve
2 - Fuel Pressure (MAP) Sensor
3 - Throttle Position Sensor/Throttle Body

I put them in this order because that the order of lowest cost (and effort) to highest cost (and effort).

I just installed a new Turbo Control Valve (I purchased a stock one, not the heavy duty version), and lo-and-behold, no more surging/hesitation on the freeway, and now the cruise control works properly. Interestingly enough it did seem to take a the car a little while to get used to the new valve. The first few hard accelerations at higher revs resulted in a pretty loud hissing noise, which I assume was the waste gate venting unexpected pressure. After 15 mins of varied driving it seems to have adjusted itself and I'm not getting the hissing anymore.

I need to drive the car a bit more to verify that this has fixed the issue, but so far so good. If it starts to struggle again once it's fully adjusted to the new valve, then I'll move on the MAP sensor.

Ian

maddog2020 · Post by **maddog2020** » 12 Jun 2014, 12:22

Well sadly that wasn't the issue, still hesitating and stumbling a little while cruising on the freeway, and dropping into limp mode under prescribed circumstances in cruise control.

I bought a fuel pressure sensor and started the work, only to find that my particular car doesn't have a fuel pressure sensor. This seems bizarre to me, but anyway. I guess if I really want to take this on I'll have to replace my throttle body now.