Toyota Tacoma Forum banner
1 - 7 of 7 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
The speedometer on my 2003 tacoma is moving but not really tracking my actual speed. Sometime it registers 0mph when I'm moving 50mph and 50 mph when I'm stopped at the traffic light. The odometer is total dead (except for the trip odometers). I replaced the sensor on the transmission and got the same issues. I checked the fuses, I don't get any check engine warnings, no ODBII codes, wiring looks OK under the vehicle. So I bought a Scanguage and plugged it into the ODBII port and it registers the correct MPH! So I think it's the gauges themselves. If I replace the rebuilt/used gauge cluster, do I need to have it reprogrammed with the odometer reading?

I'm assuming the gauge cluster has failed, since the scanguage is reporting the speed correctly? Does that make sense or could it be the ECU or something else ?
 

·
Mambeau / Admin
Joined
·
48,041 Posts
Hmmmm ... That's an odd combination of symptoms.

Does your cluster have a tachometer? If so - is it working as expected?

Is everything else on the cluster operating as expected?
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #3 ·
Hmmmm ... That's an odd combination of symptoms.

Does your cluster have a tachometer? If so - is it working as expected?

Is everything else on the cluster operating as expected?
Yes, the tach works fine. Everything else works fine.
 

·
Mambeau / Admin
Joined
·
48,041 Posts
The speedometer is a separate component, so it can be replaced without swapping out the entire cluster. The printed circuit board is also a separate component.

I'm not sure how your ScanGauge determines the speed reading that it displays. If it's simply mirroring what the Control Circuit is feeding the OEM speedo that suggests the speedo (alone) is bad. If the ScanGauge is independently calculating a speed reading without relying on the cluster's Control Circuit, the fact it works doesn't necessarily mean the speedo (alone) is bad.
 

·
Mambeau / Admin
Joined
·
48,041 Posts
In case it's helpful ...

Your ScanGauge can't be getting a speed reading off the cluster if it's a 4-cylinder.

Here (attached) is the 2003 tach cluster wiring diagram.

Notice that the Data Link Connector (OBD port) is fed by the cluster in a V6 but not in a 4-cylinder.

If you've got a 4-cylinder this means the DLC is being fed by the ECM rather than the cluster and strongly suggests it's either the cluster or the speedo that's messed up. In the 4-cyl case it would seem the speed signal is making it from the Vehicle Speed Sensor through the cluster to the ECM.

If you've got a V6, it would seem to mean the DLC is getting a valid speed signal (for the ScanGauge) from the cluster, but the speedo (the meter alone) isn't able to reliably display it correctly. This in turn suggests the problem lies in the printed circuit or the speedo unit itself.
 

Attachments

·
Registered
Joined
·
4 Posts
Discussion Starter · #6 ·
In case it's helpful ...

If you've got a V6, it would seem to mean the DLC is getting a valid speed signal (for the ScanGauge) from the cluster, but the speedo (the meter alone) isn't able to reliably display it correctly. This in turn suggests the problem lies in the printed circuit or the speedo unit itself.
Very helpful! Its a V6. If I replaced the whole cluster, do you know if the cluster needs programming for the odometer or does that come from the ECU?
 

·
Mambeau / Admin
Joined
·
48,041 Posts
I'm not sure. Like I mentioned, Toyota doesn't describe the odo functions in any of the tech documentation.

Edit to Add:

Sorry if I confused you ... I mentioned all that over in the other thread where you asked about the odo.
 
1 - 7 of 7 Posts
Top