Getting up arrow and check engine light on after repairing PNP switch Topic is solved

rgroove54 · Post by **rgroove54** » 22 Dec 2025, 08:50

Hi, I've been using this great guide - viewtopic.php?f=1&t=29930 to access and repair the PNP switch. Before starting the engine, I turned the ignition on to position II (I think) and put the car in reverse, the reverse lights came on. I was hopeful at this stage and that meant my alignment is correct? However, I get the following symptoms:

1. The up arrow and check engine light are on when the ignition is turned on to position II.
2. The up arrow and check engine light are on when the engine is running.
3. The W mode light was flashing (but E was the mode selected).

These are the codes I get:
AT-313 gear position sensor faulty signal
EFI-666 DTC in a transmission CM

Clearing the codes a few times and switching the engine off and on doesn't clear them. I connected my 850 OBDII reader to monitor the transmission in real time. I've been using it to monitor the ATF temperature during operation, it tells me what gear the car is in etc. However, I wasn't getting any reading from the transmission at all yesterday. The gear number always stayed at 4 even when going through the gears. The PNP switch info will tell you if the gear selector is in P, R, N, D etc, but it was only displaying 00 and 01 when going through the gears if I've remembered what I'd seen correctly. I did feel the transmission engage when R and D were selected, but I didn't see if the car would go forward or backwards whilst the up arrow and check engine lights were on.

Now I've repaired the PNP switch with new contacts and put everything back (I hope correctly) as it should, I'm now waiting for a replacement TCU to see if that resolves my issue, as the codes point to the TCU. I do however keep questioning the alignment part. If my reverse lights come in when in the R position, does that mean my alignment is correct?

Many thanks for any advice.

aeg · Post by **aeg** » 22 Dec 2025, 19:23

TCM is innocent until proven guilty. Car off, parking brake set, TCM removed, measure ohms from ECU box TCM connector pin A20 to each of pins A3, A4, A5, A6 in every gear selector position.

: connector.gif (31.82 KiB) Viewed 323 times

: tcm_pinout.gif (22.91 KiB) Viewed 323 times

: tcm-wiring.jpg (95.82 KiB) Viewed 323 times

Post by **ZionXIX** » 22 Dec 2025, 23:11

What was the reason for replacing the PNP switch? Was the plug clean?

rgroove54 · Post by **rgroove54** » 23 Dec 2025, 05:28

ZionXIX wrote: ↑22 Dec 2025, 23:11 What was the reason for replacing the PNP switch? Was the plug clean?

Hi ZionXIX, I was getting the up arrow and check engine lights come on when I was driving the car. The car was driving ok, gears shifting ok etc but after I stopped at a red light, the car would not pull away in D, that's when the up arrow and check engine lights come on. It felt like the car was in limp mode. Now I've cleaned the existing PNP switch and replaced what looked like worn copper contacts. When I accessed the PNP switch, I left the shifter cable bolted in place, as I was to work around it. I read that without removing the shifter cable, no re-alignment was necessary. If my reverse lights are coming on when R is selected, does that mean my alignment is correct?

rgroove54 · Post by **rgroove54** » 23 Dec 2025, 05:30

aeg wrote: ↑22 Dec 2025, 19:23 TCM is innocent until proven guilty. Car off, parking brake set, TCM removed, measure ohms from ECU box TCM connector pin A20 to each of pins A3, A4, A5, A6 in every gear selector position.

connector.gif
tcm_pinout.gif
tcm-wiring.jpg

aeg, thanks very much for this. What OHM readings am I looking for when I test each pin you've highlighted?

Post by **abscate** » 23 Dec 2025, 05:34

You are looking for continuity, approx 0 ohms.

In one step, this eliminates both PNP switch and wiring faults, so it’s high value diagnostics.

rgroove54 · Post by **rgroove54** » 23 Dec 2025, 05:39

abscate wrote: ↑23 Dec 2025, 05:34 You are looking for continuity, approx 0 ohms.

In one step, this eliminates both PNP switch and wiring faults, so it’s high value diagnostics.

Thank you for clarifying that abscate, continuity. Is that when the multimeter beeps? Apologies for sounding stupid, I'm not very experienced with a multimeter and learning as I go.

PS: great looking dog you have as your passenger. It reminds of the dog we lost a few years ago.

Post by **abscate** » 23 Dec 2025, 05:52

rgroove54 wrote: ↑23 Dec 2025, 05:39
abscate wrote: ↑23 Dec 2025, 05:34 You are looking for continuity, approx 0 ohms.

In one step, this eliminates both PNP switch and wiring faults, so it’s high value diagnostics.
Thank you for clarifying that abscate, continuity. Is that when the multimeter beeps? Apologies for sounding stupid, I'm not very experienced with a multimeter and learning as I go.

PS: great looking dog you have as your passenger. It reminds of the dog we lost a few years ago.

That’s right. Usually has a buzzer icon on the meter. Touch the leads together to check the beep. The hard part is you have to rig a long piece of wire to extend your multimeter leads from dash to engine

There is a pro trick to jump the CUT to another wire to bypass this , but that gets complicated.

CUT = circuit under test , if you use acronyms people pay you more

rgroove54 · Post by **rgroove54** » 23 Dec 2025, 07:09

Just to make sure I have this right, I'm looking down into the ECU and TCU housing and I hook up my multimeter like so and test continuity on pins A3 (jn P, R,N, D, 3, L), A4 (jn P, R,N, D, 3, L), A5 (jn P, R,N, D, 3, L) and A6 (jn P, R,N, D, 3, L)?

rgroove54 · Post by **rgroove54** » 23 Dec 2025, 08:23

I forgot to mention that my car won't start with the gear selector in the Neutra/N position, I get no crank at all. With the gear selector in P, the engine is starting with no problem and as mentioned, my reverse lights are coming on. As its not starting in N, does this mean I need to look at the re-alignment? I didn't undo these two bolts to save me from realigning, as suggested in the thread I was following. If so, could you good folks who have done this job please advise how to adjust the realignment please, even though I can start in P and the reverse lights are coming on? Many thanks.