Use L gear - get upshift & check eng lights

jb24601 · Post by **jb24601** » 20 Jan 2016, 19:26

I had a bizarre problem that I could not find on the site. FWIW, I'd like
to post my experience:
1998 S70 GLT auto
Going down a steep hill, transmission in E mode, downshifted to L. The
upshift light and the check engine light came on, throttle response became
sluggish.
Stopped, restarted the car. Throttle response came back, upshift light eventually went
out but the check engine light stayed on.
Car drove fine so I delayed going to my mechanic to pull some codes (there
had to be some). After about 300 miles, the CE light just went out. Car
runs just fine.
This has happened twice, the first time it was under warranty so the dealer
fixed it straightaway. Learned that lesson and never again used the L gear
in seventeen years, until this latest steep hill.
Never had codes pulled so maybe there's a lurker but the check engine light
is out (lights up on start though) so I say let sleeping dogs lie.
Hope this is useful.

Post by **tryingbe** » 20 Jan 2016, 19:33

Get the codes pulled.

Post by **precopster** » 20 Jan 2016, 19:50

If car drives fine in D the most likely thing would be a faulty PNP switch located on top of trans under shifter actuator.

Do get codes read though in case of a faulty PNP I don't think it will self diagnose accurately. There is a DIY PNP disassemble here on the repair database.

Post by **Ozark Lee** » 20 Jan 2016, 19:58

The up arrow light always comes on when you put the shifter in anything except drive but it should be on steady. If it is flashing that indicates a problem. Was the light flashing?

...Lee

Sommerfeldt · Post by **Sommerfeldt** » 21 Jan 2016, 04:46

Ozark Lee wrote:The up arrow light always comes on when you put the shifter in anything except drive but it should be on steady. If it is flashing that indicates a problem. Was the light flashing?

...Lee

This. The arrow also comes on when you put the tranny in Winter mode (W). W-mode basically means that the car starts in 2nd gear - nothing really fancy. Anyway - check your engine groundings as well - shifting down like that, especially if you were going a little too fast for it, might have made things move around in an untoward fashion.

- S

Post by **misha** » 22 Jan 2016, 17:05

Why you downshifted to "L" at first place?
I would understand if you needed to go UPhill with high climbing,but why for going down?That's why the brakes are for.

@Sommerfeldt...Winter mode starts with 3rd gear.

Sommerfeldt · Post by **Sommerfeldt** » 22 Jan 2016, 18:08

misha wrote:Why you downshifted to "L" at first place?
I would understand if you needed to go UPhill with high climbing,but why for going down? That's why the brakes are for.

I learned to drive from a former big rig/bus driver, who taught me to use the transmission for more than just forwards and backwards. That was a manual, but same goes for auto. I don't know about OP, but I'll use 3 to hold speed on steep-ish downhills w/speeds around 50 mph (70-90 kph) and L for engine assisted braking at slow speeds under 20 mph (~30 kph). Prevents wear and overheating of the brakes, and ups your safety level.

As for going uphill... it's an automatic transmission, so it'll downshift on its own going uphill...

misha wrote:@Sommerfeldt...Winter mode starts with 3rd gear.

I always thought it was second.

I'll take your word for it, though - I've never read up on that thing, and only used it a handful of times.

- S

Post by **Ozark Lee** » 22 Jan 2016, 19:59

Winter mode is more of a gimmick than anything that helps get through slick conditions, much like TRACS. I get the theory but it really doesn't work very well. I do take off in 2nd in the snow when I'm driving the '94 with a 5 speed and that actually works to an extent. First gear is such a stump puller on the M56L that I'm tempted to take off in 2nd all the time.

...Lee

Sommerfeldt · Post by **Sommerfeldt** » 23 Jan 2016, 04:37

Ozark Lee wrote:Winter mode is more of a gimmick than anything that helps get through slick conditions, much like TRACS. I get the theory but it really doesn't work very well.

...Lee

Yup... I looked at it a bit closer after beeing schooled by Misha up there, and it seems it doesn't actually do anything other than start you in a higher gear (3d

) to avoid spinning the wheels when it's slick. So once you get going, it can just be switched off.

- S

Post by **misha** » 23 Jan 2016, 07:18

Sommerfeldt wrote: I learned to drive from a former big rig/bus driver, who taught me to use the transmission for more than just forwards and backwards. That was a manual, but same goes for auto. I don't know about OP, but I'll use 3 to hold speed on steep-ish downhills w/speeds around 50 mph (70-90 kph) and L for engine assisted braking at slow speeds under 20 mph (~30 kph). Prevents wear and overheating of the brakes, and ups your safety level.

As for going uphill... it's an automatic transmission, so it'll downshift on its own going uphill...

misha wrote:@Sommerfeldt...Winter mode starts with 3rd gear.
I always thought it was second. I'll take your word for it, though - I've never read up on that thing, and only used it a handful of times.

- S

No need to use automatic transmission manually.These transmisions have their own tcu and they comply with driving style of a driver and road demands.
In the past,when auto transmissions were vacuum controled...on older cars....you needed to use it a bit manually.

Sommerfeldt....while you saving the brakes from overheating doing that,you're ruining your auto transmission.
Manual is another story and you can do whatever you want with it without problems.