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finding electrical shorts and more

Discussion in 'Gen 2 Prius Technical Discussion' started by elec1, Feb 20, 2012.

  1. elec1

    elec1 Junior Member

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    Is there an easy way to checks for shorts in my prius. I have an 07 won't start, I have checked the transmission plugs and there are not in specs! Manual says replace.Since this car is all most all electric its not like your cars of old.
    When it comes to tracing shorts in wiring I placed an digital meter between negative battery post but always get 12v. pulling one fuse at a time to try to pin point the circuit. This sound normal to you? The car was in an accident and wiring harness was cut in two near the drivers frame rail, repairs were done and everything seems to work. The only sensor I haven't plugged in yet was the airbag sensor on the drivers side rail, would like to get a new one since the car was hit on that side.
    I've got a few codes but since I can't get it started not sure how true there are. It will turn over but stalls, gas engine won't run, no spark at plugs, not sure Its getting fuel, car has less than 15k on it. Tranny was originally bad when I bought the car, replaced once only to find out this ones bad.
    Would like to get this car going asap, Before replacing the trans again is there anything I could check for first to try to pin point other problems before reassembly.
     
  2. andyprius

    andyprius Senior Member

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    I suspect the repaired wiring harness, but no spark points to coils ( no spark at every plug? ) Some of the fuses should show burnout. Across a good fuse you should read zero volts. Try connecting up your multimeter between the neg on the 12V and the other side to chassis ground. IN MAX Current postion. It should show milli-amp current draw. Start with highest current reading on meter and work down. Another option is to replace wiring harness with a good one from junkyard. If you remove wiring harness disconnect the High Voltage safety switch first. Ascertain that your 12V system is good. Give us some codes and sub-codes and other people can address those better than I. As for the engine, obviously you are not getting spark or fuel. Good Luck. :cheer2: PS: Another good place to check is where the major damage occurred, general body shops are excellent at not hooking everything up or not proofing a system is working.
     
  3. seilerts

    seilerts Battery Curmudgeon

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    How about all the relays? Check them. The codes are important too. Post them here.

    It is probably worth trailering the car to autobeyours.com in Indiana. It might be something simple that would take the average person forever to find, but Steve would spot in 10 minutes.
     
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  4. cnschult

    cnschult Active Member

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    i read another thread awhile back that says most people don't think to look for loose ground wires when looking for electrical problems, and a loose ground wire can lead to huge problems.

    I hope this turns out to be a cheap and easy fix for you . . . good luck.
     
  5. elec1

    elec1 Junior Member

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    All ground points seem to be hooked up. Since then I have got a code reader, codes pulled off car PO351, PO352,PO353,PO354 all related to no spark at coil tower or Circuit Malfunction. Checked wires no shorts to ground or opens. Inspected ECM (IGF Voltage Drop has higher than normal voltage readings, near 6.8V to 5.8V when cranking with IGT1, 2,3,4 disconnected, Specified Condition between 0.1v to 4.5v.
    So I take it 6.8 to 5.8 is ok?
    Problem with transmission, code reader can't communicate with transmission ECM ?
     
  6. seilerts

    seilerts Battery Curmudgeon

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    Hmmm! I suspect that there is a problem with the wire splicing which has caused abnormal readings with the ECM. It would be a significant job to put in another wiring harness, but have you considered getting one from a junkyard?
     
  7. andyprius

    andyprius Senior Member

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    There was a OP recently which did exactly that, the junkyard wiring harnesss did cure the problem.
     
  8. elec1

    elec1 Junior Member

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    Yes have my eye on one or two will pick up after Easter, hope it does the trick.
     
  9. elec1

    elec1 Junior Member

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    Is there any way to check transmission ECU and engine ECU before I pull the harness out?
    One other question, if i do need to replace ecu's do i need to have them reprogrammed? How much does the dealer charge. Someone suggested for me to buy the engine ecu with a key then your good to go, cheaper in the long run, and the transmission computer can i just swap it for a new one?
    this project car is turning out to be the money pit
     
  10. edthefox5

    edthefox5 Senior Member

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    The best way to check ECU's is to replace them. The ECU's are available on eBay sometimes very cheaply. They do not require key or code or programming but are Gen specific. If that is not the problem put that ECU back on eBay.

    The harness can sometimes be repaired if you can get to the damaged area.
    Most likely will need to have extensions put on all the wires. There all color coded. You can either use butt splice with the correct Klein
    compression tool or solder. If you don't know how to solder don't learn here use the butt splice with heat shrink tubing and heat gun.

    Heat gun and Klein butt splice tool can be found at mcm.com
    and heat shrink at mouser.com.

    Btw, when working on any Prius electrical wiring harness its a good idea to pull the Hybrid Battery Safety plug. The big orange plug in the back of the Hybrid battery housing. That disconnects the 200 Volt Hybrid battery.

    Good Luck!
     
  11. seilerts

    seilerts Battery Curmudgeon

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    The service manual is not clear on the ECM replacement vs. immobilizer ECU. It is possible that you may need to follow a learn procedure that would have the car in IG-ON for 30 minutes. On the other hand, it is not too hard to just try it.

    There are numerous standard voltage and resistance values that you can check at the ECM wiring harness, but they are scattered across the pages of code diagnostics in the service manual.

    Do you also have ABS/VSC/Brake yellow warning lights? Those codes may not show up on your reader but could be a further indication of the trouble spot.
     
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  12. elec1

    elec1 Junior Member

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    Yes have brake codes, abs codes, but i can take care of them when i get the car started, no way to bleed the air out of the system without running it on my reader. Abs pump was replaced due to repairs.
    And the airbag codes as well but due to one sensor that needs to be replaced on frame rail.
    Good point on swapping out the ECU's I did my own repairs to the harness double checked them all wires were fine before body shop work. Since im replacing the trans again i will triple check the harness again. Hate to pull it out if i don't need to.
    Soldiering not a problem, finding the short is but with everything out of the way makes it easier just time consuming.
    Hoping for the best this week if I get a chance to work on it.
    This is one project thats taking me forever to finish, to many thing and not enough time in a day.


     
  13. seilerts

    seilerts Battery Curmudgeon

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  14. edthefox5

    edthefox5 Senior Member

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    What exactly is not in spec on these trans plugs?

    If me I would get all the codes defined and see if your truly in immobilizer mode before throwing another trans at it. It could be the motor. That you still have same issue with another trans in it makes me suspicious.

    You keep saying shorts. Shorts in a car are usually blown fuses and smoke.
    If you suspect shorts go into ohm meter and with black probe on ground and Hybrid battery safety plug out ohm out all pins on harness. Anything other than a ground connection lower than one ohm is suspect. But make sure all ground pins are dead shorted to ground. You can also ohm out the entire harness this way too. Have someone ground out ta pin on one end and you measure that pin to ground on the other end. Should show dead shorted to ground. Thats the best way to find an open harness wire.

    But regarding your quote please tell us what you find on these trans plugs that are out of spec?
     
  15. elec1

    elec1 Junior Member

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    the two plug near the drivers side on the trans has no reading! took the plug off and measured the connector behind the plug, no reading in both! Plug closest to motor is within range. So I believe the MG1 and the speed sensor are bad, reason for replacement. My fist trans when i bought the car, (salavage) was missing plugs and the MG1 was also shorted. My fault for not bringing a meter when i picked the first transmission up, then it just sat there till i had free time to put it in. By that time the warranty had expired.
    For now I picked up a new trans at the yard and an ecu for engine. Wiring will be rechecked again. I did find two wires going to the speed sensor that were mixed up there were grounds. Rest of harness checked out ok, everything seamed to work except no spark at coil wires. All wires were checked back to plug at ecu confirmed good. Ecu voltage out of range while cranking 6.8v.
    I don't know maybe i missed a ground wire? rechecked all connections twice upon reassembly!




     
  16. elec1

    elec1 Junior Member

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    Re: At last some headway

    Had found a lose ground wire replaced trans, started at last, battery charging.
    Codes I still have, C1247 Stroke Sensor & C1310, hope they go away after I bleed brakes.
    B1615, B1801,B1811 and B1901 pretty sure due to a missing drivers side air bag sensor.
    After 10 minutes car stalled not much of a throttle response but no engine codes? ABS & VSC lights lite and a triangle with exclamation point.
    Code reader can't read transmission ecu?
     
  17. seilerts

    seilerts Battery Curmudgeon

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    Well, there's some progress!

    The car stalled simultaneously with a red triangle alarm? There should be a code for that. You can always disconnect the 12V and start over. It won't fix any of those B or C codes but might make it easier to spot the actual fault if it stalls again.
     
  18. elec1

    elec1 Junior Member

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    Well I thought the car was stalling, just turned out the gas engine turned off, hey what can I tell you its my first prius!
    Now to bleed the brakes, another adventure.


     
  19. seilerts

    seilerts Battery Curmudgeon

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    :welcome:

    You most likely will need a scan tool to bleed the brakes and do a zero point calibration. C1310 is probably there because you have C1247. C1247 has many causes -- do you know for sure that you need to bleed the brakes? You could try doing a reset first, jumpering pins 4 and 13 of the DLC and, with the car in Ready, pumping the brake pedal 8 times in 5 seconds.
     
  20. elec1

    elec1 Junior Member

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    Yes body shop pulled my abs pump off, messed it all up had to replace it, pissed me off big time. Not sure if the resets even an option at this point. Have an Autel MD801scanner its does air bags and brakes at least it says it does, we will see. Can't find my password for it to login?