Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Light issues, probably electical

I have an electrical issue with my 2004 Saturn Ion, and with everything shut down, I figured I’d try to fix it myself, if possible.

It started out with what appeared to be my front, left (driver-side) turn signal going out. Easy – I replaced the bulb. But that didn’t work. I checked the connector at the light and it seemed fine. So I just hand-signaled for a while.

Then, after a little while, the dashboard’s left turn-signal indicator started lighting up whenever I pressed the brake.

So I decided to do a full check of the lights, and they are all sorts of messed up (see below).

I’m guessing there is an electrical problem somewhere, with a switch or a relay or a wire. I check the fuses, and they all appeared good.

I understand I will probably have to check throughout the car to find the problem, but I was hoping I might get some guess on where to start based on the symptoms, which I will list below. Any suggestions would be greatly appreciated.

I do have a Haynes Repair Manual with the wiring diagrams, so I should be able to follow along with that.

Run-down of which bulbs function, when. (Apologies in advance, I don’t know for certain what each bulb is called and couldn’t find a clear explanation anywhere – so some of my terminology may be inaccurate). Also, it’s possible I wrote some of this down wrong.

Left (driver) Front

  • Inner bulb (main headlamp)
    —Works under all circumstances (other than headlights turned off)
  • Outer bulb (turn signal [and parking light, I think])
    —Works when headlights are on alone
    —Turn signal – does not flash
    —Hazards – does not flash

Right (passenger) Front
-Everything works fine

Left (driver) Rear

  • Top bulb
    —Lights when headlights are on
    —Does not get brighter when brake applies (not sure it is supposed to, though)
    —Turn signal – flashes fast
    —Hazards – works
  • Middle bulb
    —Lights when headlights are on
    —Gets brighter when brakes applied – if headlights are off, see note*
  • Bottom bulb (back-up light, I think)
    —Doesn’t work (might just be burned out coincidently, I haven’t tried changing it)
  • *All – when headlights are on, all left rear lights go out when brake applied

Right (passenger) Rear

  • Top bulb
    —Lights when headlights are on
    —Does not get brighter when brakes applied
    —Turn signal – works normally
    —Hazards – works normally
  • Middle bulb
    —Lights when headlights are on
    —Gets brighter when brakes applied
  • Bottom
    —Lights up when in Reverse

Thanks again in advance for any help!


PS – If you think I’m going to need any electrical tool other than a multimeter, let me know.

Have you checked your battery?

Your careful and logical approach will work. Use that circuit diagram and look for the power or ground that connects the turn/hazard light fixture with the turn signal switch AND the hazards switch.

Sounds like one or more bad grounds.

Big mistake!

Don’t ever trust a wiring diagram in a Haynes manual

They’re wrong!


Clean all bulb sockets with light sandpaper.Insert new bulbs and make sure you do not touch the glass part with your fingers.Use disposable gloves for this purpose. In my experience, if one or two bulbs goes bad,the rest of the lighting system can sometimes work erratically.It was the case with my old Ford Tempo.

All the lighting in your vehicle is controlled thru the Body Control Module.


For the 2004 Saturn Ion Lighting systems, GM shows different schematics for early production and late production. I don’t know what the production date dividing the two is, but the front lamp wiring harness shows a division at VIN 4Z159356.

The early production systems used what are called splice packs for connecting the lamp ground wiring together. They look like a regular wiring connector, but are plugged into a jumper bar (for lack of a better name) that connects all the connector terminals together (see pic).

The later production design eliminated these splice packs in favor of a basic soldered splice within the harness(es). If this vehicle is an early production and grounding issues are causing the problems, the splice packs should be checked for corrosion or other issues. The splice packs are located as follows:

Splice Pack SP101 (Early Production): In the forward lamp harness, in the left front of the vehicle, near the left headlamp
Splice Pack SP401 (Early Production): In the body harness, in the center of the rear shelf, near the left rear speaker
Splice Pack SP403 (Early Production): In the body harness, in the center of the rear shelf, near the right rear speaker

There was a TSB (04-08-42-002A) for “Turn Signal Indicator Flashing Faster than Normal and Corresponding Front Turn Signal Bulb Inoperative”, which seems to apply to your left side. This TSB was superseded by an actual recall (#04095) for “Daytime Running Lamp (DRL)/Turn Signal Bulb Replacement and DRL Jumper Kit Installation.” This covers 2003-2004 Ions within VIN ranges 3Z100001 - 3Z207807 and 4Z100063 - 4Z232317 (last 8 digits of VIN). You can check your VIN at your dealer to see if it is affected by this recall and if so, if it was ever repaired.

Thanks for the feedback, everybody!

The battery is fine, and I think all the TSBs and recalls were taken care of, either by me or the previous owner, but I can double check.

Seems like the order of approach should be:

  1. Check the grounds.
  2. Check the connection between the light fixture and both the turn signal switch AND hazard switch.
  3. Check the body control module (and make sure I get the right kind for my VIN if it needs to be replaced).
  4. If no clear problem with grounds, connections, BCM; try cleaning the sockets and trying new bulbs.

As for the Haynes manual, well, I gots what I gots - but if you have a recommendation for a more reliable wiring diagram, I’ll look into it.

Thanks again for the help, everyone!