Issues with dash lights

[UncleGlen]

Had to (mostly) remove dash to remove HVAC blower motor. With minor exception everything went better than expected.

After testing of the blower motor, and reassembly of dash to normal, I noticed the parking brake light flickering. At first I thought loose connection, though not sure where... but after some additional observation, i feel like there is something more...

the light flashes rhythmically almost like morse code...

e-Brake works, and light stays lit while engaged.
e-brake disengages, and seems to release just fine... just get this light blinking on/off.

all other systems seem to work, including a number of things unplugged b/c of dash removal.

thanks!

1990 GMC Sierra K1500 SLX 5.7L Manual.

 

[Schurkey]

Some vehicles, that dash light does triple-duty. Comes on with park brake. Comes on when brake hydraulic system safety switch is triggered, and comes on when ABS is unhappy.

Count the flashes--short and long. If I'm remembering correctly, my '88 K1500 used to get "Code 9" fairly often. It can be a "false" code. The service manual has diagnostics.

 

[UncleGlen]

Thanks for the info. Found my Chilton manual and looked at a few other interwebs responses...

solution... since the error does in fact sometimes relate to uneven pressure in lines, and the cause (so sayeth the interwebs) is air in lines... I checked fluid levels... (duh) Low fluid! Added fluid, tested line pressure per other recommendations and after reconnecting battery and starting... I got one "flash" from brake light and then no more blinking... so without a lengthy test ride period, looks good for now.

thanks again.

 

[evilunclegrimace]

Find out where the fluid went!!

 

[Deereone23]

Why do I, have a service engine soon yellow light coming on after driving 10 minutes on my 1993 GMC C1500?All fluid levels are fine.
Also have a red brake light on all the time.It glows brighter if I apply emergency brake pedal.

 

[Schurkey]

Why do I, have a service engine soon yellow light coming on after driving 10 minutes on my 1993 GMC C1500?All fluid levels are fine.
Also have a red brake light on all the time.It glows brighter if I apply emergency brake pedal.

Because there's something--and probably multiple somethings--WRONG. This requires diagnosis and repair of the problem(s).

In particular, the red BRAKE light serves multiple functions--it comes on with the park brake, it comes on with the hydraulic "Safety Switch", and it comes on with a fault in the ABS. Make absolutely sure that both front and rear brake hydraulic circuits have pressure when the brake pedal is pushed, and that the ABS works properly.

Connect a scan tool, check for engine/transmission/ABS "codes", but also look at the data stream to verify sensors and computer outputs. You'll need that scan tool to properly bleed the ABS unit, which likely has not been done since the truck was manufactured.

 

[Deereone23]

This is pre OBD.

 

[Schurkey]

my 1993 GMC C1500?

This is pre OBD.

Of course not. On-board computers--and scan tools to diagnose issues with them--go back to 1980 1/2.

It's pre-OBD2, but a proper scan tool will still pull heaps of information out of those computers.