S90 PNP Switch replaced still have AT-124 error

jrf0007 · Post by **jrf0007** » 16 Sep 2012, 09:47

1998 S90 with 208981 miles started generating errors: EFI-666 DTC in transmission CM & AT-124 Mode selector switch, signal too low with no change in car performance--transmission still shifted normally when in drive. Classic indicators (up arrow on dash (transmission fault indicator) and flashing W & E on mode seletor) for pnp switch malfunction were on continuously--but otherwise car ran and shifted normally. As state inspection is due this month I replaced the pnp switch. Now have same error indicators plus the transmission is not shifting when in drive.

While replacing the pnp switch the car side of the wire harness connector to the pnp switch pulled apart---wires intact but pulled out of the connector. Insulating material on all 8 connectors had disintegrated. I reconnected to new pnp switch by matching wire sequence/position number from wiring diagram with numbers on connector (car side wires and pnp switch side wires do not match by color). Note one wire (black) on car side harness does not match to wiring diagram. Lt Blue wire in wire diagram does not have matching wire on harness--I assumed the lt blue and black wires are one and same and installed black wire in position 3 on the connector. I used tubing I had on-hand to make insulators for each of the 8 connections. I positioned the switch so that back-up lights come on when shifter is in reverse.--at least that wire pairing must be correct! I'll check the connections against the wire colors on the old pnp switch to see if there are better color matches.

Here are my questions:

1. Can the pnp switch position cause the transmission not to shift and still be providing back-up ligthts signal?
2. Is it likely I have the wire harness wired incorrectly and that is the cause of the transmission shift issue and the AT-124/EFI-666 codes?

Other engine codes have since developed, too. Here are all the codes that are currently generated:

EFI-666 DTC in transmission CM
EFI-612 Fuel tank system small leak --I think this is just the gas cap not tightened correctly
EFI-233 Long term idle air trim
AT-124 Mode selector switch, signal too low

pegas_group · Post by **pegas_group** » 13 Mar 2013, 08:03

For EFI-612 Fuel tank system small leak there is a vacuum line running form your engine back to the fuel line pressure regulator. There there is a rubber piece and you have to replace it with vacuum hose from AutoZone orxxx.

I can send you a pictures.

Any Luck with AT-124 Mode selector switch, signal too low.

When AT-124 is cleared the EFI-666 will go away.

Regards
Nick

pegas_group · Post by **pegas_group** » 13 Mar 2013, 08:42

The EFI-233 Long term idle air trim means that you have some vacuum caps on vacuum tower dried out. and they are leaking. By some vacuum cap kit from HF and also replace all melted vacuum rubber connectors.
If you have small vacuum leak it will be noticeable for the ECU under low rpm (idle). if is slightly bigger the ECU cannot regulate the Idle rpms and will set EFI-233. Also look for loose vacuum hose connection in Idle stabilizer valve.

Regards
Nick

pegas_group · Post by **pegas_group** » 13 Mar 2013, 20:42

More

DTC information

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.

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 symptom
The transmission operates in driving mode E.

st_Andy · Post by **st_Andy** » 20 Nov 2015, 10:26

Please try to put another ground minus - cable between battery and engine, just connect the battery minus pole with any part of engine or open car skelet and try to start, if it starts then check the ground (minus) wire from the battery to the transmission! I had the same issue with
AT-124 error code and it was just a rusty connection between the battery and transmision

Hope it helps