Is there a scanner to diagnose as well as the OEM Toyota equipment - Topdon?

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Josh Dalrymple, Jul 27, 2026.

  1. Josh Dalrymple

    Josh Dalrymple Junior Member

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    II
    I have a persistent problem I am trying to diagnose, but independent shops around me don't touch hybrids, and Toyota techs seem to follow a script without actually looking. Case in point, I had reached my wits end trying to diagnose a misfire. No coolant leak, new coils and plugs. Took to dealer, said needed a new longblock after claiming to do a compression check. Didn't look like the plugs had been removed to me, as I had put them in. Jump forward, I installed a new JDM engine swapping over all original sensors, plugs, injectors etc., but still had the misfire. I swapped one component at time and misfire disappeared when I put in the JDM fuel injectors so my original engine was misfiring due to the injectors, not low compression. Ever since the swap though, my high temp coolant light is on, even from a cold start. I can also monitor engine temp with a scan tool and it shows warming up nicely to 190 and not overheating. Also occasionally, about every other time driving I get a dashboard full of lights: Hybrid system, Antilock, check engine, slip indicator, and the permanent high coolant temp. No codes are set, and I can clear the lights through clear codes on the scan tool. Are there any better scanners to diagnose a Prius. I suspect the hybrid battery is weak, but why the coolant temp light since the swap?
     
    #1 Josh Dalrymple, Jul 27, 2026
  2. rjparker

    rjparker Tu Humilde Sirviente

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    Disclosing your current scan tool would help.

    The first step is to know what your engine has in your problem area and then monitor it. Otherwise the gold standard latest graphical Techstream won't help.

    Since there are two engine coolant temps, one of them is not being monitored and could be the issue. The second is downstream of the exhaust heat recirculation system and could be simply unplugged.

    ehrs flow and sensors partial.jpeg
    Two coolant temperature sensors with "Car Scanner" app designators


    engine dual coolant temps techstream.jpeg
    Legacy Techstream coolant temperature sensors


    Exhaust Coolant 7C0 and Engine 7C4 Temp Sensors.jpeg
    Car Scanner app realtime data


    Exhaust Recirc Sensor Closeup.jpeg
    Pic of second coolant temperature sensor

    Concerning Toyota hybrid capable apps, Techstream GTS+ is the best with ecu download and bidirectional test procedures in addition to live data and dtcs.

    Image.jpeg

    Various bluetooth elm327 apps do a reasonable job of live data and dtcs including Car Scanner. Dr Prius is not one of those good apps for all codes.

    Most shops have a several thousand dollar bidirectional Autel or Launch scanner which are also the base software for other brands like Topdon and even Harbor Freight's high end scanner.

    The Autel AP200 app with proprietary bluetooth dongle is capable of most codes and realtime data for under $100. I found it slow with no graphical trends, just a low dollar subset of Autel's best software. Not bidirectional as well.

    A recent value oriented scanner video from Pine Hollow Diagnostics had one Launch based bidirectional bluetooth scanner selling for $100 or less.


    Amazon link
    https://bit.ly/4pJhLnO
     
    #2 rjparker, Jul 27, 2026
    Last edited: Jul 27, 2026
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  3. Josh Dalrymple

    Josh Dalrymple Junior Member

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    Your post was most helpful. A bluetooth elm327 dongle and Car Scanner app led me to the issue and it is now resolved. Thanks.
     
    #3 Josh Dalrymple, Aug 2, 2026 at 2:59 PM
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  4. 2015V-BadHG

    2015V-BadHG Junior Member

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    So please tell, what was it?
    thx, Pete
     
    #4 2015V-BadHG, Aug 2, 2026 at 6:41 PM
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