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97 2.4l extra cab manual trans #🌮⏳
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Discussion Starter · #1 ·
So I got some led lights.
Well I did center high mount on my camper. Like it. Them did headlights, liked it more
Added some driving lights- oh I glow light xmas.
Well my hvac was not lighting up. So pulled that, and ordered some cluster bulbs while I was in there. Ran my switch for driving lights to the far side.
Well now the srs light stays on dimly at all times when truck is off or on. Thoughts?
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Mambeau / Admin
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(1) Does the ignition have to be 'on' for the SRS light to shine dimly?

(2) I'm not understanding the 'switch to the driving lights' bit at all, so I don't know what's been moved to 'the other side'.

(3) Here (attached) is the '97 SRS wiring diagram. The warning light in the cluster is wired in-line from the 15A ECU-B fuse to the Airbag Sensor Assembly (the SRS 'brain'). The lamp's circuit also happens to be cross-connected to the DLC1 within the 3A connection.

Two things come to mind. The first is that the LED lamp's resistance is so low that it glows just because it's in-line on the power feed (fuse) side of the sensor assembly.

However ... I can't figure out how the lamp is activated in the first place. If it's in-line in the power feed line one would think it should be constant-on unless something inside the sensor assembly activates that circuit's connection to ground. Toyota historically prefers negative switching - i.e., closing / switching the circuit on the grounding side of the component / unit rather than on the power input side.

The second thing that occurred to me is that in (re-)running wires you somehow disconnected one of the two ground lines from the sensor assembly and you're getting some sort of mild current feedback on the circuit in which the lamp is wired. The sensor assembly has 2 ground lines - one each running to the right and left kick panel ground points. Without knowing what's going on inside the sensor assembly I have no idea how realistic this theory may be.

The first thing I'd do is swap the SRS warning lamp back to an incandescent bulb to see if that fixes the odd behavior. If it doesn't stop the warning lamp glowing that probably means the fault isn't just a matter of a sensitive LED bulb.

Hope this helps ...
 

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97 2.4l extra cab manual trans #🌮⏳
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Discussion Starter · #3 ·
That was what I was gonna try, just did not want to have to pull it all apart again.
I put in led driving lights, and wanted the switch on the left side of cluster, this was my draw to pull the cluster, that and I got the size 74 bulb for the hvac head and the pack was like 10 bulbs for 8$.
Oh well, I'll pull it back apart and swap back to incandescent.
Maybe shoot a hyperlapse of the teardown to upload for disassembly steps for folks lol.
yes @Enola Gaia your diagram and mine from Mitchell show negative switching though the srs unit. Thinking it's just bleed off voltage and the led does not draw off the circuit enough. (Shrug)
 

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