Hi folks

Can anyone help me figure out what is causing my '96 850 automatic transmission to go into limp home mode within five seconds or so of being placed into Park? If I avoid Park (start and end in Neutral), I can drive around all day with no issues, although Low will sometimes trigger it. The code is invariably for a fault with the PNP switch.


So far:
replaced and adjusted PNP switch (twice)
replaced transmission CPU
adjusted shift cable at the transmission end
replaced (ugh) transmission with claimed good unit from salvage yard

Again, the code is set by putting the transmission in P (and sometimes L) only. No other issues, shifts great, can drive all day.

Anyone have any ideas?

First, I'm wondering if you have a solenoid issue in trans. Are there any codes at all? Second thought is the shift lock switch located under the Consol. Wonder if a fluid flush might clean things up.

Second the flush idea. Suggest using the cheapest ATF you can find for the flush then refill with synthetic ATF recommended for an 850 transmission. If you aren’t using it already, synthetic ATF has been known to do wonders for automatic transmissions. Especially after a flush…

--
Will I buy another Volvo??? We'll see....

Hi,,
First off I’ll let you know I don’t know anything about the 850. As far as that goes not much more newer than my 1993 240. 🙂

I curious though as to why or how you know it’s not something else besides a limp mode activation?
Is there a specific code that comes and goes each time or dies it just run lousy at low idling speeds.

I would wonder if it isn’t an EGR problem as they are only supposed to get activated during idling.
A EGR code may be too generic or in its temperatures isn’t swinging enough to trigger it.

A little air in the wrong places at the wrong time might appear as limp mode.

The Park and Low gear selection does throw some wrenches on the floor though?
Later automatics did get into lot of solenoid trickery.

Keep us updated.

Phil

The simplicity of a 240 is a thing to behold!

I don;t have any engine issues with this car, just this infernal transmission problem.

Additional data I have shows faults--all the time, even when the transmission is operating properly, for:
MSEL (The mode selector switch) ERROR (and I have replaced it with more than one that an ohm meter says work properly, and:
GSEL POS (Gearshift lever signal position) ERROR

But there isn't much in the gearshift lever in the way of electronics, so I don't know what the code means!

Thanks for looking!

Hi,

Yes the simplicity of a 240 is something to behold and I have been beholding the six of them since 1978.
I bought them all used though-out the years when the opportunity or a need to get another happened.
I figure that they were all so similar in design that one could devour the other to keep any one of them running for the rest of my life.
Well it looks like they may make themselves available for two lifetimes.
I slowed down using them up with age but gave them a good try.

I can remember when Volvo claimed that they were not interested in building FWD cars. Look what happened the liars!
Sales does govern all the manufacturing minds or they ruin themselves in other ways. Volvo is an experiment that’s been in progress for a very long time.
The 100 and 200 series had a very very good run because they thought of ways to make it more user friendly and dependably reliable in several sectors of ownership. Ownership is fading faster than ever.
Volvo has lost site of that concept in order to be a fashionable car company for stock holders first.
Simplicity and longevity are not valued like they once were.
The Hand Me Downs way of thinking has just about been obliterated for future generations.

So no issues with the engine operation!
I see now …duh, where you are talking about being in limp mode is actually referring to the transmission only. So you say it limps with the power it gets from the engine?
I have never experienced that one!

I wondered how the fuel management system ever got involved with the transmission.
With that out on front street I see your dilemma. Is it integrated into a speedometer?
The 700’s had special speedometers too.

Somehow they must have a selector mode switch telling the ICU or the ECU conflicting information.
This item must also work with a speed sensor to know if the car is moving or not.
On the last productions (92+) of the 240s they tried different speedometers signals in doing some sort of idle controlling, that I have not experienced but have read about it.

I’m wondering if what you have going on, is a failure to communicate in a certain sequence. 🤔 it sure seems so.

You know that’s one thing that us 240 people have come to realize is one low voltage signal pin in a connector or a weak ground can raise hell with diagnostics as in “intermittent.”
Your problem appears to be electrical and most likely in that realm mystery.

You say it works fine if you keep it out of the Park detention. Then occasionally, the low gear selective makes for trouble.
That is the right way to observe things, IMHO.
A man’s hand causes things to break or wear out because that’s the nature of things.
Something that is well used is now breaking down.
It does fine you say and I think you said you exchanged the transmission so what the chance of two identical things happening twice?
Sure appears to be that a connection can be made that it didn’t get changed.
I would seriously look for a wiring connector or the wiring itself especially in the console where things get nasty down there.

Yep, you are going to need lots of patience and perseverance.
Keep that thinking cap on, them eyes open and you will find it!

Phil