Howell EFI check engine light in stock...ish position - JeepForum.com
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post #1 of 9 Old 10-12-2018, 05:59 PM Thread Starter
defmornahan
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Howell EFI check engine light in stock...ish position

I had my Howell kit installed by a shop just under 4 years ago. They did some pretty weird things, including sticking the check engine light all the way over by the passenger side door.


I was swapping the heater core and had the whole under-dash out, so I narrowed my beady little eyes at the check engine light and decided its time had come. I looked at the install instructions and called Howell for good measure...the pain in the butt part of the system, why they recommend getting a rando light from Radio Shack instead of wiring into the existing check engine light, is that the GM circuit has hot to the check engine light while the key is on and links up the ground when it wants to turn on the light.


I pulled out the indicator light assembly and traced out all the circuits on that film that goes from the connectors to the wires. In my 1987 Wrangler, there was a common ground servicing 8 of 12 terminals (including three with empty sockets), another one for 3 terminals...and one little unused terminal with its own ground. Bingo. I moved the check engine light bulb over to that spot (see photo) and did some surgery with scissors, tape, and glue to move the CHECK ENGINE window over the new bulb. If you count conductors you can see that its feed and solitary ground are wires 4 and 5 (on the right side when the part is mounted on the jeep).



At that point I needed to scavenge two wires from somewhere and move them into the proper spots in the connector, and then splice those to the Howell SES (service engine soon) wires. You would think I could grab the check engine light, but you'd be wrong. Some PO seems to have removed that wire from the connector already. However, I was in luck:


There was a stray orange and black wire in the outside socket of the right hand connector. Org/blk usually feeds the gauge lights, but this is socket 8 of the connector and there are only 7 prongs on the other side...it wasn't connected to anything. (To have been a fly on the wall when AMC was deciding where to source parts for this beast.)


There was also an upshift light, brown with blue tracer (one of the prettiest wires in the harness, really). This was available for two reasons:
  • Automagic transmission on this bomber. (In fact it has a column shift like Grandma's Caprice. Were they all like that? How many factory automatic 1987 Wranglers are there? Three?)
  • Even when I drive a stick, like Dad's GM 2500, I frankly don't give a crap what your opinion of when I should shift is.
I got probably excited and ended up loosening the whole fuse block, cutting the brn/blu wire there, and pulling it all the way out of the harness. That took quite a while, but it's enough wire to reach all the way over on top of the heater where they stuck the Howell computer. I wasn't as aggressive with the orange with black tracer wire, largely because it just goes back into the harness with 17 other org/blk wires and good luck tracing that, so I got a length of stray black wire to suture in. The second photo shows the right side connector with the center two wires newly placed, and the third photo shows what they're hooked up to on the Howell wiring harness.


Obviously, you'll need to check your jeep's wiring to make sure this will work. I haven't tested mine yet...not only was I replacing the heater core, but the thermostat and the seals on the gas tank as well, so the jeep is not quite operational tonight. I will report back.

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post #2 of 9 Old 10-13-2018, 12:31 AM
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You have a shift indicator light? That's odd.

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post #3 of 9 Old 10-13-2018, 05:08 AM Thread Starter
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I assume that's what the big up arrow is. I'll try to post a picture.


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post #4 of 9 Old 10-13-2018, 05:43 AM
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Quote:
Originally Posted by defmornahan View Post
I assume that's what the big up arrow is. I'll try to post a picture.
That’s what the big up-arrow is. I’m not 100% sure- only judging on jeeps I parted out before I got to know ‘jeep’ a little bit from this forum- but I think 87-89s, maybe 90s, too, all had the upshift light but it wasn’t connected for autos.

Also, there were quite a few 87s sold with an automatic trans. Not most. There was a post somewhere with production numbers, maybe not jeepforum though. I just looked and couldn’t find- only that 45,000 1987 jeeps were produced.

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post #5 of 9 Old 10-13-2018, 08:12 AM
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My 88 has a shift indicator light, but it does not work. I think it was 4 cylinder only.

If I'm reading your post right, couldn't you have just used a relay to swap the polarity for the check engine light and called it a day?

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post #6 of 9 Old 10-13-2018, 09:49 AM Thread Starter
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Originally Posted by zrickety View Post
My 88 has a shift indicator light, but it does not work. I think it was 4 cylinder only.

If I'm reading your post right, couldn't you have just used a relay to swap the polarity for the check engine light and called it a day?

I don't think I needed to swap polarity for anything. These are old school incandescent bulbs.



The problem is that the Howell has two wires: a pink lead from "hot when ignition is on" and a ground that closes when the GM computer wants the SES light on. Meanwhile the old check engine light position is on a common ground along with the 4WD light and the brake light (as well as the upshift light and seat belt indicator... another wire I could have stolen). The old computer hooked to the carb, or if the Chilton wiring diagram is to be believed just a nag timer for emissions work, would feed the check engine light +12V when it wanted the light on.



If I had just attached the pink line to the check engine light, it would get +12V and be on whenever the key was on.


If I had just attached the brown line to the check engine light, it would have been ground to sometimes ground and the light would never come on.


If I had attached the pink line to the check engine light and the brown line to the common ground, the check engine light might have worked, but the 4WD light and brake light would only ever come on when the check engine light was on.


If I had attached the pink line to the common ground and the brown line to the check engine signal connection, the check engine light might have worked, but the 4WD light and brake light would never come on...the signal would be +12V and it would hit +12V from the pink line and no current would flow.


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post #7 of 9 Old 10-13-2018, 09:57 AM Thread Starter
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It lives! If you need proof: video



Here's a picture of my indicator plate after cosmetic surgery.


Stupidly satisfying to have this done.
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post #8 of 9 Old 10-13-2018, 11:11 AM
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Hmm, either mine doesn't have that up arrow, or it doesn't work and I've never noticed the spot. Interesting.

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post #9 of 9 Old 10-13-2018, 11:47 AM
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Originally Posted by defmornahan View Post
I assume that's what the big up arrow is. I'll try to post a picture.
No, it's telling you which way the jeep is supposed to be. It lights up when you roll it on it's side.

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