24v-12v OBD2 adapter

I’ve been wanting to try this for a while. Quite often I’ve seen Isuzu heavy duty engines listed in the menu of cheap 12v scan tools. Recently my Launch CRP123X showed that it had an update for Isuzu. After it had done the update I had a look and saw options for Isuzu N and F series trucks with 4HK and 6HK engines among others. But since it is only a 12V scan tool that is pretty pointless to have if it can’t be connected to those trucks. I contacted the supplier who confirmed it could not be connected to 24 volt systems.

But since it is only pin 16 which has battery voltage, and the communication voltages are all the same for 12 and 24 volt systems, I ordered a cheap 24-12V converter and wired it up in line with the power supply pins of an OBD plug.

obd24 (1).jpg

Today I had the chance to test it. A 2010 Isuzu Forward was in our workshop and I plugged in the converter, then plugged in a 24v scan tool to make sure that it confirmed “12v module present” and then plugged in the 12v Launch CRP123X and went into "“Isuzu, 6HK1-Euro 3”. It got into the ECU, read fault codes and showed live data. I just chose barometric pressure sensor voltage and ECU voltage which showed at 24.9v which was the reported ECU voltage, not pin voltage. I tried accessing ABS and SRS but couldn’t get in but am happy to be able to scan the engine computer at least.