Speedometer, gas gauge failing intermittently


#1

2005 Scion xA 127,000 miles

Total nonmechanic here.

Problem started with speedometer not working occasionally. Now it works about 75% of the time. Often if I park for several minutes and restart the car the speedometer will work again. Sometimes after I start the car at first it won’t work. Then I hear a click and a whir and it works.

Recently the gas gauge has been failing occasionally. I start the car and the needle doesn’t move. I restart the car immediately and it works.

Only once the tachometer didn’t work at first. Then the needle jumped up suddenly.

I found at least 14 possible causes online:

  1. Relay
  2. ECU
  3. Loose wire or connector in cluster
  4. Speed sensor
  5. Fuse
  6. Gauge
  7. Electrical short––recalibrate speedometer
  8. Faulty speedometer head
  9. Bad transducer
  10. Dirty connection
  11. Body control module (BCM) hung up
  12. Bad ground
  13. Bad stepper motor
  14. Bad alternator diodes

QUESTION 1: Given that the problem has gotten worse over time, it’s intermittent, and now two gauges are involved, what’s the most likely cause?

QUESTION 2: A garage told me it’s illegal to buy a used instrument panel and have the odometer reset. Is that true?

QUESTION 3: If not illegal, what’s the cheapest way to get a reliable IP and get it reset? I can’t afford a new cluster at a dealer.


#2

In that vehicle…I would say that it is the cluster itself. That cluster has no mechanical connections at all…its all computer driven and electronic.

If I were you…I would pop out the cluster and unplug and re-plug in the connectors on the back of that cluster to see if you can “scrub” the contacts and make a better connection. Aside from that…there could be a “cold” solder joint somewhere in the cluster needing attention.

Most of this stuff is outside the ability of the regular guy to be able to repair…not sure what your background IS…but you said you arent a mechanic…and that doesn’t matter here. You need to be an electronics guy to handle this one methinks.

You can send the cluster out for repair if you dont see any better options for getting a new one. I cant think of anything else it could be since there are multiple issues across different systems inside the cluster. You surely arent having multiple simultaneous sensor failures within the vehicle.

The ONLY other thing i would look into is your GROUND connections…at the battery…and also on the body. You can also look into the fuse box under the hood…make sure the wires heading out of that box are tight. But yes…the ground connections could be a culprit too…

Blackbird


#3

Thanks very much, Blackbird. Very helpful. I have zero mechanical ability. I’m trying to educate myself before I take the car to my mechanic. He hasn’t examine the car yet. He was thinking it was a sensor but that was before the gas gauge started acting up as well.


#4

@Tailwind

Use your own judgment, but there could be another very unscientific thing to try that could offer a clue for the mechanic. Don’t ask how I know this.

When a gauge fails to respond use your open flat hand to rap the top of the instrument panel above the instruments. If you get a response then that should help indicate where the problem is.

Items such as the BCM and others aren’t generally located in the dashboard.
CSA


#5

“When a gauge fails to respond use your open flat hand to rap the top of the instrument panel above the instruments. If you get a response then that should help indicate where the problem is.”

+1
While many people think that this approach went out the window after the '40s, it can actually work on vehicles made much more recently.


#6

I agree with the flat hand technique…but that method has little chance of helping when multiple gauges are failing at the same time…multiple failures suggest the problem is deeper. But yes…I have beaten up many a gauge to see if it jogs it back to work.

Blackbird


#7

i vote that it’s the connection in the back of the cluster that is corroded or loose.

I may be wrong but, I thought that the mileage numbers were held in the PCM (Powertrain control module) and that all that is in the cluster is the display. If this is true, the cluster from a junker would display the miles on your PCM not the car it came out of.

Yosemite


#8

All ideas above are good, and worth trying. But before I tried any of them, I’d first make sure the battery and charging system were working correctly, the battery is fully charged, and has clean and tight connections. All of that is quite easy for your shop to do. Shouldn’t produce much of a bill. They do it all the time.


#9

I’ve slapped the top of the instrument cluster many a time, believe me. Didn’t help a bit.


#10

As to the legal issues with replacing the IP, that probably varies state to state. The state’s role is to insure that the car’s mileage be accurate in the event of a future sale. Ask this at a local shop, they’ll likely know the answer straight away. It seems like there’d have to be a way to replace the IP legally. Might have to get the DMV involved though.


#11

Most vehicles mileage is a function of…and stays resident ON…the cluster itself. But in theory the odometer reading could be telegraphed to the cluster from the ecu…but I’ve never seen that happen. Every one i have seen the numbers stay on the cluster itself

Blackbird


#12

I Know That On Some Chrysler Cars The Mileage Is Stored In The BCM. When A Dealer Orders And Replaces A BCM They Take It Out And Impound The Car Until The New Unit Arrives And Is Installed. I’m Pretty Sure They Don’t Want a Fine.
CSA


#13

On the vehicles I’m familiar with, the mileage is stored in the cluster

I think installing a used cluster is a REALLY bad idea. It might show way more mileage, and it might also be on the verge of failing

If the problem isn’t an OBVIOUSLY bad solder joint or loose connection, I think the best solution is to have the cluster sent out to one of those shops that specializes in such things. If you google it, you’ll get many hits

The best thing about this approach . . . nothing was really modified. So no need to program and/or initialize the cluster at the dealership. Believe me when I say this . . . your typical cheapo aftermarket scan tool will NOT do that.


#14

Here’s some information from a shop that reprograms odometers:

http://www.prospeedo.com/pro80.htm

You might find something useful. My guess is that your cluster can be repaired, and you probably want a professional to do it. Even if they replace the instrument cluster, the shop will reprogram the odometer if it isn’t automatically reset. Talk to a couple-a-three specialists near you and see what they say.


#15

“I’ve slapped the top of the instrument cluster many a time, believe me. Didn’t help a bit.”

That’s because you have a Japanese-made vehicle with a fairly good degree of competence in its design and manufacturing. By contrast, I used to know a woman who had an Audi TT (vintage 2005 or so), and she had an ongoing problem with the windshield wipers not activating when she turned the WW switch.

After many repair attempts, she was told by the shop foreman at the Audi dealership that the only sure way to get the wipers (and possibly other components) to function properly with those…wonderful…cars was to slap the top of the instrument panel very firmly whenever you want something to function. He even showed her the exact spot on the top of the instrument panel that should be hit in order to get her Audi to function properly.

German engineering…You’ve got to love it…