1998 S70 PnP switch 9466012, bad aftermarket new part Topic is solved

ferocity02 · Post by **ferocity02** » 30 Jan 2018, 10:57

I have a 1998 Volvo S70 GLT that I've been having an ongoing issue with. Every now and then, the transmission will throw an error for low signal from the transmission range switch, code AT-124. This is accompanied by a check engine light and the transmission getting stuck in 3rd gear. This seems to happen most often when parked. It rarely happens when driving.

First, I took apart the factory switch, cleaned the contacts and filed them back to shape. This did not make much difference.

Then I replaced the switch entirely with a new non-OEM part. This sort of worked. The issue became less common after this, but not totally gone.

About a year goes by without any trouble and it just started acting up again, and it's doing it quite often, every other day roughly. This suck because I have to smog soon and I can't pass with a check engine light.

Anyone have any suggestions?

Post by **wizechatmgr** » 30 Jan 2018, 11:25

I'd test both old and "newer" switch to see if either is good with a multi-meter. The problem with intermittent issues is they're damn hard to nail down during testing.

ferocity02 · Post by **ferocity02** » 30 Jan 2018, 12:34

Like you said, because the issue it intermittent, I can test all day and never have see an issue. I did test both at one point and they were fine.

Some searching suggested that it may actually be an issue with the S/E/W drive mode swtich. If the TCM loses signal from it for 25 sec it will throw the same code. So I'm going to see about cleaning this switch tonight.

Post by **wizechatmgr** » 30 Jan 2018, 13:37

Couldn't hurt

Post by **FLXC90** » 31 Jan 2018, 06:44

Makes sense, mode switch is in a likely position for contamination by spills. If it goes into W mode, there's your third gear start

Post by **RickHaleParker** » 31 Jan 2018, 16:18

I think you got an intermittent short that puts the transmission in Winter mode.

43: AT-124 Mode selector switch

DTC information

A4300770 Condition
The driving mode selector allows the driver to select from three modes: Winter (W), Economy (E) and Sport (S). The mode selector has two signal cables, MS1 and MS2, and a ground lead. Driving mode is selected by connecting one or the other, or both signal cables to ground (the signal goes low). Note that MS1 and MS2 signal cables are grounded simultaneously only when the W button is depressed.
B=battery voltage
G=ground (Ulow)

Diagnostic trouble code (DTC) AT-124 is posted if the transmission control module (TCM) registers that the signal is low (low voltage) in both signal cables simultaneously for at least 25 seconds.
Caution! This diagnostic trouble code (DTC) can be posted if the W button is depressed for more than 25 seconds
^^^^ a short could do this ^^^^^^

Substitute value
The transmission will only operate in driving mode Economy (E).

Possible source

Short-circuit to ground in signal cables
Defective mode selector.
The W button has been depressed for more than 25 seconds.

Fault symptoms
The transmission operates in driving mode E.

Post by **BEJinFbk** » 31 Jan 2018, 19:19

FLXC90 wrote: ↑31 Jan 2018, 06:44 Makes sense, mode switch is in a likely position for contamination by spills. If it goes into W mode, there's your third gear start

For this very reason, my console is virtually always
protected with a small, charcoal colored dish towel...

It may not show off the pretty fake wood trim,
but if my coffee sloshes, I'm good!

ferocity02 · Post by **ferocity02** » 11 Feb 2018, 19:56

Ok guys... I tried holding the "W" button down for 25 seconds and it did not error out the transmission. Not sure what to make of that... I went ahead and replaced this switch anyways and I got the AT-124 error again a couple days later. The original was clean inside.

The last time I saw the moment the transmission errored was as I was putting it into park. So today I messed with the alignment of the PNP switch. With the switch rotated all the way to one side, I recreated the AT-124 error where putting it into will park with throw the code, several times. So I rotated it all the way to the other side and no error. Reverse lights still work. It's not aligned perfectly but I'm going to give it a shot. So far so good.

ferocity02 · Post by **ferocity02** » 12 Feb 2018, 13:20

The AT-124 code came back...

Things I've tried so far:
-Cleaned PNP switch
-Replaced PNP switch
-Adjusted PNP switch
-Replaced S/E/W mode switch
-Checking wiring and connections at these switches

The fault is intermittent so it's a real pain to diagnose.

Any more ideas? Need to smog soon but can't with the Check Engine light. When I smogged 2 years ago the transmission faulted DURING the smog test. Of course the transmission waits until smog time again to start acting up.

Post by **RickHaleParker** » 12 Feb 2018, 13:35

Probe for shorts in the cable to the mode selector.