I've taken on the task to troubleshoot the Brake Light Safety indicator light which is always on. This is the light on the instrument panel, just below the door/trunk ajar indicators, and NOT the BRAKE light on top that indicates low fluid/e-brake. I have checked all 5 bulbs, and used an ohm meter to ensure I have continuity through all the bulbs at the left & right brake light sensor connector. I've gone as far as pulling out the dash instrument panel and the left & right rear brake light sensor units to access connectors and check for loose wires/connector problems (no problems). I also tried (unsuccessfully) to bypass the Brake Light Sensor & bulbs by grounding the wire that goes to the instrument panel from the Right rear sensor connector. I am using the electrical schematics from the 1990-1993 Haynes Repair Guide, and I've noticed some differences that are not mentioned anywhere else on the internet:

First, I see some problems with the Haynes guide schematics:
1. The left & right Brake Light Sensor Units (the ones attached to the tail light assemblies) and wiring are reversed from the Haynes schematic. In other words, on my 1993 LX 5 door wagon (KQ model) the sensor for the 3 bulbs is on the left (schematic shows right side), and 2 bulb sensor is on the right side (schematic shows left) The WHT-GRN wire that sends the ground signal to the dash when all bulbs are working properly comes from the Right side tail (schematic shows left) I've found a similar year (90-93) Sedan at the junk yard, and noticed the sedan car matches the Haynes schematic. Just thought I'd mention that as its a strange find... Unsure if the wagon is wired different, or if there was a change for the 1993 model vs the Haynes book)

2. Also seems to be different pin outs for the connectors into the instrument panel, as I was trying to trace the brake light sensor wire that goes to the Instrument panel. Book schematic says it is pin C4 (which I assume is the big 22 pin connector, pin 4). But the white/green wire I am tracing from the '3 bulb sensor' on the right rear is going to a different pin on the big C connector.

Can anyone confirm that this problem exists... and do you have the correct schematics or connector pin-out's for the 1993 LX Wagon?


Now for my troubleshooting problem;
It looks like the stop light sensor circuits will provide a ground signal to the dash instrument cluster when all the bulbs are working properly, thus, I should be able to unplug the connector and just ground the WHT-GRN pin (pin 1) going to the instrument panel. Is this Correct?

Alternatively, I should be able to ground the pin at the connector into the Instrument cluster as well, and if that doesnt work, then the problem is in the cluster.
Does anyone have a schematic of the instrument cluster itself? I figure I can try to re-solder a cold solder joint, but it would be nice to know where to aim instead of hitting every joint.

FYI.. Ive had this car since 'birth' in 93, and its been exceptional all these years (and only 130k miles!!). Having this light on is more of an annoyance, and it just looked like a nice challenge to fix it myself

 

First, I'm moving this to General Tech. The "DIY" area is for written-up instructions, not troubleshooting questions.

Then...
I think those sensors are sensitive to wattage, not just continuity. Sometimes a bulb that is getting ready to fail will get brighter or dimmer, and will not match the wattage it's "supposed to be".

 

PS... Without a circuit diagram, this is just a guess. But I bet the sensor provides a ground when it wants to light up the warning lamp. Not the other way around. Traditional Honda way of doing those things is the lamp always has a hot lead, and the ground is switched.

 

Jim,

I agree; though I'm trying to bypass the bulbs & sensors to troubleshoot. The schematic looks like the (right) bulb sensors will provide ground to the instrument panel when all left & right brake bulbs & relays are engaged. I'm trying to bypass the sensors, bulbs and wiring by grounding the proper pin coming into the instrument panel. Schematic points to "C4" which appears to be the big 18 pin connector on the lower right of the instrument cluster, pin 4. But when I check the connector, the pin outs/wire colors do not match the schematic pin-outs.

I'm trying to find the right wire. I see a WHT-GRN come in to the 18 pin connector at the instrument cluster, which is supposed to be the wire from the tail sensor unit, but I'm finding that wire always grounded, even when I pull both connectors from the left & right light sensor units. This doesn't make sense to me, so I'm going to go back and recheck my steps.

 

Update: I found the correct wire C4 (WHT-GRN) going into the instrument cluster and shorted it to ground, but the Brake Bulb light still remains on after turning on the ignition. So it must be the instrument cluster that has a problem. I could really use a schematic for that instrument cluster! Anyone have experience opening these up and working on the electronics?

 

What happens when you disconnect that wire (so it's not shorted to ground)?

 

By Honda service troubleshooting guide, with the WHT-GRN wire into the dash not grounded, the BRAKE BULB lamp will remain on when turning ignition from off to on. I'm trying to get the indicator to turn off.

Honda's troubleshooting recommendation is to just ground that WHT-GRN wire off the right rear connector. Of course I get the same results doing that. I went for the instrument panel connector to eliminate the wiring harness as a potential problem.

 

For those holding on with baited breath... I resolved my problem..to the dashboard instrument panel component level. Problem was a capacitor that leaked, and corroded a 1/2" square on the dash circuit board. After cleaning it up and replacing the 4 caps in that circuit (unsure which one actually leaked), it is all working well again

The 'good to know' for this old car is I figured out how the brake bulb light works, in great detail. Grounding the pin from the right rear tail light connector will cause the break bulb light to go out when turning ignition from off to on (after the 5 second 'self test' beep beep)

The schematics are good except the left & right bulb sensor circuits & wiring are reversed in the Haynes schematic, too. I reverse engineered a schematic diagram of the door open/Brake Bulb circuitry. If you want a copy, let me know