1994 Saturn SC1 Speedometer

Tiny
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  • 1994 SATURN SC1

Electrical problem
1994 Saturn SC1 4 cyl Front Wheel Drive Manual

I have a 94 saturn sc1, just recently the speedometer stopped working. So far as I know the wiring in the dash is fine, no fuses are blown, and the speed sensor is ok. I dont know what to look at next.

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Thursday, September 23rd, 2010 AT 8:11 AM

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Tiny
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How do you know the speed sensor is good how did you test it?Also do you have a any code's?You probably have a bad seat belt module under your center console that control's your power seat belt's. The speed signal has to go threw that module before it get's to your speedometer.

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Thursday, September 23rd, 2010 AT 1:30 PM
Tiny
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I completely switched out the speed sensor for a new one and it didn't make a difference. The only code that comes up is 26 which the book says is the quad driver module. I've also checked the TPS with a volt meter and that seems to be working fine. However this is the first time anyone has mentioned anything about the seat belt which have occasionally been acting up. The only thing they are doing though is rolling back when the key is in and turned to run. That and the chime for the lap belt starts. This only happens occasionally though.

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Thursday, September 23rd, 2010 AT 2:57 PM
Tiny
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The seat belt module is part of that quad circuit and a bad one will set a code 26 and or a code 27 quick quad fault. The reason the speed signal goes threw it is because when the car reaches about 13 mph the power seat belt will close if the drivers door is open if the seat belt doesn't close and the seat belt close's other wise then you have a bad seat belt module.

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Thursday, September 23rd, 2010 AT 3:16 PM
Tiny
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Makes sense, is that something that can be checked with a meter or anything? And how would I go about repairing it or replacing it

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Thursday, September 23rd, 2010 AT 3:25 PM
Tiny
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They way I check them is put the car up on the lift with the front wheel's off the ground with the driver's door open put the car in drive and spin the wheel's to about 20 mph and if the drivers power seat belt doesn't close then you have a bad seat belt module. If you have a jack and jack stand's you could raise the front wheel's off the ground with the ebrake on and the rear wheel's blocked. Why don't you do that to see if the seat belt close's and let me know what you find and we will talk about what to do next.

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Thursday, September 23rd, 2010 AT 11:50 PM
Tiny
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Ok so I did that and it seems to work how its supposed to. Pretty much as soon as I hit the gas the belt closes. Whats next?

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Friday, September 24th, 2010 AT 11:37 AM
Tiny
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Alright the speed signal is going into the seat belt module but we don't know if the signal is coming out of it. The problem i'm having is I can't find a wire diagram for the speed signal circuit to tell which wire's go where if memory serve's right I think it goes from the seat belt module to the inside fuse box to the speedometer. The way I always test it is I have a tester seat belt module I swap it with most of the time it work's and tells me that the old one is bad. Let's try this under your ebrake handle pull your ebrake all the way up. You will see a access door pop that off then look into the hole you will see a black box that is your seat belt module see if it's cracked or all sticky and look's like thing's were spilled on it. Let me know what you find.

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Saturday, September 25th, 2010 AT 12:09 PM
Tiny
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Ok so I've found a black box with the letters TRW On it. It is cracked and covered in dust and crumbs but not sticky at all.

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Saturday, September 25th, 2010 AT 10:45 PM
Tiny
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I emailed you some wire diagram's let's try this unplug the connector to the seat belt module that has the dark green wire with a white tracer on it the wire will be terminal H labeled on the connector. Then see if your speedometer work's. Let me know what you find.

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Sunday, September 26th, 2010 AT 4:43 PM
Tiny
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I have a hard time reading the diagram, it shows up kinda blurry. I could not find anything that was labeled with an H and two of the connectors have a dark green wire with a white tracer on it. I tried disconnecting them one at a time and seeing if the speedometer worked but it still did nothing.

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Monday, September 27th, 2010 AT 1:11 PM
Tiny
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It say's to print it for better viewing try unplugging both dark green wire's with white tracer's at the same time and see if the speedometer work's.I see a speed input going into the seat belt module but not one coming out so what I think happens is when the module's take out the speed signal that it just sap's that signal down so the speedometer doesn't work. Let me know what you find and we will go from there.

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Monday, September 27th, 2010 AT 1:27 PM
Tiny
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I printed the diagrams, They are still fairly blurry, however im not sure i'd be able to understand them either way. I disconnected both the connectors with the green wire and white tracer and tried it again. Still nothing

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Monday, September 27th, 2010 AT 1:51 PM
Tiny
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http://www.2carpros.com/forum/automotive_pictures/416332_1994_SC1_speedometer_diagram_1.jpg


I'm also emailing you a copy of the wire diagram that i posted.The speed signal run's from the pcm to the inside fuse box then it split's off to the seat module, cruise control and the speedometer.Your going to have to remove the dash top there is two dash cover cap's that cover the screw's pop those off.Then remove the screw's there 7mm then work a big flat headed screwdriver along the outer edge of the dash facing you and pop up the retaining clip's.Make sure you stay close to the retaining clip's when you pop then up.Then you will tilt the top up and slide it out of the of the slot's that are by the windshield.I emailed you how to test if the speed signal is getting to the speedometer instead of using the cruise cluster tester which you don't have you will have to spin the wheel's on jack stand's while checking the dark green and white wire for voltage.You have a bad speedometer or your not getting the speed signal from the inside fuse box.

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Monday, September 27th, 2010 AT 3:46 PM
Tiny
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I found two green and white wires again. I tested both of them. One did absolutly nothing. The other with the car on and idling had about.003 for the voltage and increased when in gear and gas was pressed.

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Monday, September 27th, 2010 AT 4:43 PM
Tiny
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It say's that you should have half of your igniton voltage to that wire. It look's like the wire your looking for is terminal A on the cluster connector so that would be the end one. It sound's like you have a break in the wire from the inside fuse box to the cluster.

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Monday, September 27th, 2010 AT 8:19 PM
Tiny
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Ok and what would be the easiest way to find and fix that problem

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Monday, September 27th, 2010 AT 8:34 PM
Tiny
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What you should find with the key in the lock position check the dark green and white wire the one on the edge of the connector which is terminal A with the cluster unplugged it should read battery voltage.That is the speed input for your cluster.Now if you go to the back of your inside fuse box you will see large black 68 way connector above that there is a smaller connector with 4 dark green wire's coming out of it.Unplugged it then put your multimeter on low ohm's scale like the 200 ohm setting.Check between the A terminal at the cluster connector with it unplugged and the C terminal of the small connector the terminal side of the connector.Let me know what you find.


http://www.2carpros.com/forum/automotive_pictures/416332_1994_SC1_speed_signal_wire_diagram_1.jpg


I also emailed you a copy of the wire diagram so you can see the terminal's.

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Tuesday, September 28th, 2010 AT 7:27 PM
Tiny
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Sorry it's taken a few days to reply. Ive had to work a lot and couldn't get around to my car. However the multimeter I have only has ohms volts and something else would it still work for this or do I need to buy a different one? Also could u help u help me out with understanding which is the A terminal and the C terminal?

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Monday, October 4th, 2010 AT 12:40 PM
Tiny
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Your volt ohm's meter will work for testing start by putting it on dc volt's then with the key off unplug the cluster you will see two dark green wire's with a white tracer one will be the last wire on the end of the connector like I told you before. That is terminal A on the cluster connector that should have battery voltage. Now put the meter on ohm's and check the reading from terminal A of the cluster connector to terminal C of that other connector I told you about the connector should be labeled.

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Monday, October 4th, 2010 AT 1:21 PM
Tiny
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I tested terminal A with the key off and it's giving me about ten and a half volts. With the car on it gives 12 volts. I'm having trouble with terminal C though. Does it need to be unplugged too? Or can I just insert the pin in with the wire while it's plugged in? Doing it that way gives me a reading that jumps all over the place from.339 to 155.0 and the measurement switchs between M ohms and k ohms

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Monday, October 4th, 2010 AT 2:19 PM

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