Pete 379 96 wires

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Kenllah, Apr 21, 2021.

  1. Kenllah

    Kenllah Light Load Member

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    Nov 17, 2017
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    I have two wires to the front of the enging 3406e but they are oem peterbilt. What do the go to? 20210421_214830.jpg 20210421_214843.jpg
     
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  3. Kenllah

    Kenllah Light Load Member

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    Nov 17, 2017
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    The truck didn't come with a low coolant warning sensor but there is a light on the dash when you turn the key. Was hoping one of these wires was the key to installing a sensor in the radiator tank.
     
  4. RocketScott

    RocketScott Medium Load Member

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    Tacoma, WA
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    239 is a ground wire
    242 is switched accessories
    Neither are specific to anything in particular. 242 powers lots of things and 239 grounds a bunch

    I believe the water sensor should be A98 for the signal, and 98 goes to the light on the dash. Not sure what all the options were for those engine shutdown systems or how they were wired
     
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  5. Kenllah

    Kenllah Light Load Member

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    It's ecm disabled. No warning, no shutdown, nothing. Would like the dash light to work if possible
     
  6. RocketScott

    RocketScott Medium Load Member

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    You'll need a module/brain of some sort for the light to work as designed

    My truck doesn't have an ECM so there's an ISSpro that only monitors water level. There are modules that also monitor other things like oil temp/pressure

    Try to find a wiring diagram for your ECM. I don't know enough about cats to tell you for sure but the diagrams that came up for me show a four wire sensor that tells the ECM whether the water level is normal or low. It only shows two dash lights ('check engine' and 'warning') but has some other outputs that might be able to be programmed to light the low water lamp
     
    Kenllah Thanks this.
  7. Kenllah

    Kenllah Light Load Member

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    It appears that the idiot lights & gauges other than check engine & warn engine have their own sensors & switches outside of the ecm circuit. I replaced all 7 cat engine sensors and the harness. There is no cat option for low coolant that I know of, just high temp. That will flag the check engine but the water high temp light runs off of a single wire switch in the thermostat housing.
     
  8. Kenllah

    Kenllah Light Load Member

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    I found a schematic. Looks like there are several ecm inputs basically for engine protection and or shutdown. Wire A98 is one of the options but it is disabled in the ecm since the truck did not come with a coolant level sensor. I'm guessing the wire is there somewhere and could be connected to a sensor. The dash warning light is there and lights up on initial key turn.
     
  9. RocketScott

    RocketScott Medium Load Member

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    Tacoma, WA
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    Check the pass through connector on the firewall. A98 should be on the right side second from the bottom on the engine plug

    Check the pinout for the ECM connector and see if those wires are there. Also look for a 4 pin connector on the engine with orange,white,yellow,pink wires. They usually make one harness that can be used for every possible configuration. The unused wires could be bundled up and zip tied back by the ECM
     
  10. RocketScott

    RocketScott Medium Load Member

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    If you add a low water sensor to the ECM I have no idea if it will work automatically or if that option needs to be turned on by someone that knows how to program the ECM. There are "multi-function" outputs on the ECM. One of those might be able to be run to the dash light but, again, you'll need someone that knows how to program the ECM to do that. I have a cummins mechanical engine so I can't help with that

    The other option is to get one of these (or something like it):
    ISSPRO.com
     
    Kenllah Thanks this.
  11. Roger McG

    Roger McG Light Load Member

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    Oct 22, 2016
    western mass
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    Your Pete has a factory harness to the cab and gauges and the cat engine harness to the ecm for your engine controls. 2 sets of sensors so a low coolant circuit to the ecm would do nothing to send signal in cab or to warning panel in dash
     
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