HELP! 155ma Parasitic Draw on 12v battery isolated to OBD2

I have a 2009 Prius Gen 2.

I have had a parasitic current draw for 155ma and tired of fighting 12v battery issues.
I get this draw with the key cancel switch in but read on.

I have disassembled my dash and unplugged most everything searching for the cause AND:
The 155 ma parasitic current goes away when the 7.5a OBD fuse is removed OR I unplug two of the middle lower connectors on the back of the inside J/R #1 with the ECU Body is on the back side.

With the two connectors plugged in and the fuse removed I can measure continuity from the fuse output side to the OBD2 battery pin as well as the Center Connector No. 2 Inner Circuit wires 12(5M) and 13(5H) to the right of the radio.

With both connectors and fuse unplugged the 12v battery wire to the OBD2 pin should be isolated as far as I can see in my 2006 diagram. However, it measures about 200K to ground, which tells me it goes somewhere else or there is a short.

The 2006 wiring diagram suggest that this OBD 7.5 a fuse also powers “Engine Control” and “TOYOTA Hybrid System”. I can’t find what and where those circuits are located. I tried looking on the pages referenced and nearby pages - 128 & 92.

I have not found a 2009 Prius wiring diagram, just the 2004 and 2006 wiring diagrams.

Please help! Where else can I look?

 

Good questions. The car does have an SKS FOB, but the key is far away indoors AND the proximity key dection is turned off with the key cancel switch. In addition, the 7.5 A OBD fuse being inserted or removed should not affect the proximity key detection.

 

Appreciate your thoughts. If I buy a 2009 wiring manual, I will likely buy a paper manual such as is found on eBay. I DO like that Toyota’s diagram is interactive as you described.

i agree with your thoughts. I thought about removing one of the two wires from the J/B to determine which side had the “shunt” parasitic draw, and I also thought to just replace the whole length of wire with a separate wire and see what stops working. Remember though, both middle connectors on the rear side bottom of the ECU body/JB #1 have to be removed, or the fuse, to get rid of the parasitic draw. I don’t understand why this occurs, perhaps that is a clue to the problem or the additional circuits alluded to drawing current from the OBD fuse.

I did replace the ECU body/JB#1 with another, no change.

 

You must be an electrical engineer, as I am. I had thought about the 200K measurement, and decided it was likely an active circuit not a pure resistance. As the voltage rises above what my meter is supplying, the current rises much faster.

I carefully inspected and cleaned (with CRC circuit cleaner) the OBD connector and the middle junction box pins. I also measured no shorts to adjacent pins in that junction box.

I will go look up which connector is 1L (after taxes are complete) and think about that.

 

i understand precisely what you mean. I used three different meters, and yes, I have blown the fuse or current shunt in meters before.
I make my measurement between the negative battery post wire and the chassis ground. To make a precise measurement, I parallel a jumper between the two and my current meter, wait for the current to step down to its lowest value, and then remove the jumper. The meter showed the 155ma. I also used a cheap HF 10a scale meter without the jumper in parallel, and wait for the current to drop to its lowest value of 0.15 a. When I pull the OBD fuse, the current drops to 0.001 or 0.000.

I should mention that I have ALL the fuses and relays removed from the fuse tray in the engine compartment, and all the ECUs on the passenger side, and all the displays, and the radio/DVD. I have at times pulled the brake box next to the 12 volt battery, the connector to the key ECU and the passenger side air bag, and also all the relays and connectors on the drivers side inside fuse block. So when I say the current drops to nothing, It is awfully close to nothing! I do have to plug in those 2 lower middle connectors on the back side below the body eco to have the parasitic current draw.

 

Because I have so many plugs, relays, fuses removed my current is close to zero when I pull the OBD fuse.
There is nothing plugged into the OBD connector.
I have no aftermarket devices, I bought this car used and believe it to be stock.
We think alike about seeing what stops working with the OBD fuse removed. I have everthing torn apart and hesitate reassembling all to try this now, but eventually will if nothing else surfaces. Now that I think more about it, I could just reassemble just the electrical stuff and try it. (After taxes)

 

CORRECTION: It was not both plugs, it was only the larger of the two middle connectors (1L) and pin 5, just as in the Toyota wiring diagram.

So, I am thinking to cut the wire at 1L and at the OBD connector and replace that entire run with my own wire. I finished my taxes so back focused on my Prius. I also think I will follow the wire as much as I can looking for any overheated or chaffed wiring first (but not taking much of the black electrical tape loose) Stay tune!

 

i know about corrosion (aka green crusties) which can be conductive. I have looked for it as I disconnected fuses and connectors or wiring, and not found any. It is not surprising, as this Prius has been in Colorado and New Mexico which are dryer climates.

I think I will segment the wire at the central junction box as I have nothing to lose by doing so. Who knows, the “short” could be inside that box.

As for trackers, I haven’t seen any but it could have had one that was removed, and left a bare wire that could short to something else. When I do a close inspection after segmenting, I will be on the lookout for such.

 

I found this device, which is strange because all but two of the wires (red and black) to it are cut,





I did a search using the part number (see picture) and I believe it is a GPS tracker. Here are some links with the FCC data including a user manual and a picture that looks the same. The user manual shows the current can run as high a 1 amp to power the GPS receiver and cell phone connection.

OET List Exhibits Report

https://apps.fcc.gov/eas/GetApplicationAttachment.html?id=2717937

Red&Black wires appear to be power connection, so I will track them down and see where they connect. Stay tuned!

Update: found this searching for the FCC id:

TALONCV001 CDMA vehicle tracking device User Manual TALONCV001 _Rev 2 Montage Systems, .

 

It was connected to the 12v pin on the OBD connector. This picture shows the ground connection after electrical tape was removed. The +12 v connection was similar. I removed both connections and then measured the parasitic draw……GONE! (I taped the stripped wires well)

Now to reinstall everything and hope I haven’t caused any new problems. Stay tuned…