Speedometer Going Whacked!

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Junior Member
Ok. Now something weird is going on. My check engine light has been on due to me using only one o2 sensor which is normal. But now my speedometer isnt working right. It moves when car is just idle'n. It jumps from 0 to 50/60/70mph while idle'n. Have you ever heard of such a thing? It also doesnt show me my "real" speed when driving. It just stays at 0 until it feels like jumping. I've tried to reset the ECU by disonnecting the battery several times. The other weird thing is that the Check Engine light kinda dimms and gets brighter now. It didnt do that before. The car runs fine though. Could my ECU be bad?
first the ecu is not broken at all
the first place u should check is if the speed sensor on you tranny is not disconected
this is located on the rear of the tranny below wear your intake meets up with your
throttle body, u should replace the sensor first before doing any thing else, if this does not fix your problem then your speedo gauge is broken [rare problem] or have put any aftermarket wires or gauges in the car.
remember check the connection at the speed sensor, clean it, and reconnect, replace sensor if nessassary and then look at gauge cluster.


Junior Member
Ok. I checked the connections. They are all fine. I also jumped the ECU to get the error codes. I'm getting error #20 which is ELD. One more thing i forgot to mention is the speedometer doesnt jump and the lights dont dim untill i give the car gas. If i just start the car and dont touch the gas, the speedometer doesnt jump at all.
u say its code #20, electrical load device
have u shampoo'd your engine lately?
if not then i will look at the the circut diagram at work on monday, but it may be the [eld] but may be just a blown fuse causing more power to go thru another system to make up for the short circut
is your car a civic with a engine swap?
what year civic?
the [ELD} elerical load detector is located under your under-hood fuse box, its on the bottem of the box, take look at the box for bad wires , and blown fuses,
take the fuse box apart flip it around and look underneath for bad wires also
mice like to sit there at night and eat the wires,
tell me what u see so i can tell u more


Junior Member
My car is a 1997 Honda Civic DX. I put a new stock motor from a 1999 Civic in it about a month ago. I'll check the fuse box tomarrow when its light out. I would also like to know the pin outs for the o2 sensor. If two of the wire from the o2 sensor touched could it of damaged my ECU?


Senior Member
You have a bad ground.

Check your grounds and clean them if necessary.

I guarantee this is the problem. And I'm about 90% sure it's the ground at the thermostat.


Super Moderator
also when your alt. goes out, your speedo will trip out. the charging system is on the same circuit as the speedo.


Senior Member
Hey man I had exactly the same problem with my 96 civic. It took the dealer three times to get it fixed but it turned out the problem was a short in the wire at the back of the engine. You might check the fuse box and find two fuses out thats what happened to mine the second time to the dealer, but you might have to dig a little deeper to solve the problem. When I had this problem the speedo/odo stopped working, the engine light came on and all the accessory lights dimmed.


Junior Member
Ok. I checked all ground. All were ok. Then i checked my fuse box under the dash. I found the Alternator fuse blown. Replaced it and everything seems fine now. :D Thanks to all for your help. I would never of thought to look at the alternator fuse for that problem. Now i just need to figure out how to get rid of the CEL due to having headers and only one o2 sensor plugged in. Thanks again.