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Engine temperature display problem, options?

3K views 5 replies 3 participants last post by  Ottoman 
#1 ·
hey guys,

Need some opinions/options pls

I recently picked up an 09 premium AT with 35k bone stock except the tires.

It has the typical fuel float issue. But also it has a problem where the coolant temp on the instrument cluster is always stone cold and never moves when u key on/off


I figured it was the sending unit so I bought a new one. I plugged the new one in and no dice. :(

I'm not getting any codes either.

So I'm guessing the ecu is getting the correct input from the sensor so it's not complaining. And the problem lies in the cluster itself

Does anyone have any idea if it is a serviceable sub module or the whole IC would need replacing is there any benefit to me opening the dash and yanking the cluster and trying something with it? Or am I stuck at the mercy of the stealership?

I don't have a scan gauge or ultra gauge to read the obd II port and see if it can pull the data. But I would like to get it working either way.

Any help is kindly appreciated. Thanks
 
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#2 ·
Did you take a look at the electrical schematic to get an understanding of the interconnections between the sender on the engine block and the gage itself in the instrument cluster?

Schematics can be downloaded from the purefjcruiser.com website at:
http://www.purefjcruiser.com/docs/FJ-Electrical-diagrams.pdf

Once you digest the schematics, you can start the usual electrical troubleshooting process of looking for opens & shorts in the wiring harness, verify power is present where it is supposed to be, etc.
 
#3 · (Edited)
Thanks, I'll wade through it some more and see if I can find something that will help. So far the diagram shows the temp sensor basically terminating to the ecu.

I was thinking though. The whole cluster gets power signal ground everything through only 2 plugs. Considering the fuel and voltage gauges are working fine. They probably have shared power/grounds and independent signal inputs. (Well that's my theory at least)

The cluster looks like one big integrated circuit. And might not be fixable :(

I'm starting to worry maybe it's the stepper motor or something:(


*edit*

yup, i went the FSM, (EM-51) for those wondering

it looks like the Temp sender->ecu-> gauge cluster..
they don't speak directly

manual says if sensor is good, and the wire between cluster and ecu is good..

then Sux to be you, change the cluster or "combination meter assembly" as they call it..

looks like I might have no choice but the go to the dealer.. and have an extra temp sensor for nothing too

*sigh*
 
#5 ·
Yes, the temp sensor itself is terminated at the ECU, and the ECU provides the signal to the "meter" in the gage cluster ("combination meter" in Toyota-speak).

Did you check for continuity of the signal line between the ECU & gage cluster? The schematics identify the various connectors between ECU & gage cluster, and I'd de-mate, inspect for corrosion, and then re-mate all connectors, including those right at the gage cluster.

If you had any type of OBD monitor you could independently verify that the temp sensor is providing valid temperature data to the ECU, and eliminate sensor, sensor wiring & ECU as suspects. Normally a shorted or open temp sensor will trigger an OBD code, but ....
 
#6 ·
yup thats next on the list..

the problem is I recently moved to Mexico, and sold all my tools and everything before coming.. I went and cobbled a basic kit together of craftsmen hand tools.. to do some basic maintenance and work and stuff

a good DVMM and obd II reader wont be cheap..

the ECU is in the passenger foot well and clear across the cabin from the cluster harness... its gonna be quite a reach for the DVMM


i'm wondering if i might end up spending more time and money trying to fix it (with no guarantee of success) then I would just letting them do it...


decisions decisions...
 
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