Signal ground has continuity with Chassis ground when ECU plugged in.

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D-Oaten
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Joined: Mon Aug 06, 2018 12:48 pm

Signal ground has continuity with Chassis ground when ECU plugged in.

Postby D-Oaten » Mon Aug 06, 2018 1:04 pm

Hey guys, so i've been working with haltechs for a while and haven't yet encountered this issue before.

So a customer brought me a Suzuki samari with a 2jz vvti crammed into it and needed his elite 2500 wired in. So I wired it with a flying lead harness and got the engine to fire up no problem on a base map. But i kept having an issue with the CTS reading Max+Min and throwing a code. Tried different toyota sensors, haltech sensors, even tried running the CTS off a different AVI and signal ground wire, no change.

We had a mechanical water gauge so we attempted to get some steady state tuning done before any power stuff and right away the tuner told me the readings on the ECU didn't match the numbers in the real world. So after a bunch of digging in the engine harness i found that when the ECU is plugged in the Signal ground wires have continuity with the chassis ground, but when i unplug the ECU and test all the signal ground wires for continuity with the battery or chassis there is no continuity.

I'm wondering if this is my problem with the other sensors reading incorrectly and also throwing off my CTS sensor, or is it normal for the Signal and chassis ground to have continuity when the ECU is connected?

Anyone else have similar problems?

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HaltechMatthew
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Re: Signal ground has continuity with Chassis ground when ECU plugged in.

Postby HaltechMatthew » Wed Aug 22, 2018 12:52 pm

Yes they have continuity when the ECU is connected. They just shouldn't with the ECU disconnected. This is because the ECU is providing the ground via a 0-ohm loading initernally.

red dragon
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Joined: Sun Aug 26, 2018 3:04 pm

Re: Signal ground has continuity with Chassis ground when ECU plugged in.

Postby red dragon » Sun Aug 26, 2018 3:31 pm

OK I own the truck and downloaded software off usb key. Pluged in laptop clicked connect and the wire melted between the laptop and ecu. Not sure what to do now. All i wanted to do is change then the fan turns on. Could the wiring to the engine have something to do with this.

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Drwaffles
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Re: Signal ground has continuity with Chassis ground when ECU plugged in.

Postby Drwaffles » Sun Aug 26, 2018 9:35 pm

As Matt said, signal ground will eventually go through to earth internally, completely normal. Current need a path to flow, it just doesn't disappear.
Signal ground is very simply just a shielded earth that you connect your sensors too get a clean signal and have good reliable data.
What are the sensor values? Have you setup the diagnostic tab under CTS. Have you enabled pull-up?
Very hard to help with minimal information and not actually seeing the install.




I'm a little confused how the wire melted? USB is usually limited to 5 volts and typically 1-2amps max, not really enough to melt unless it's extremely thin wiring.
Didn't leave a soldering iron sitting on it or something?

red dragon
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Joined: Sun Aug 26, 2018 3:04 pm

Re: Signal ground has continuity with Chassis ground when ECU plugged in.

Postby red dragon » Mon Aug 27, 2018 9:29 am

Plug in lap top with the wire that came with the haltech used usb key to download program, clicked connect and usb melted and wire melted. I was there in person to watch one mechanic plug in the shop laptop and check the fuel pressure very simple. This is what i did. No soldering iron or other tools. The ignition was on engine not running fuel pump fuse pulled out. Is it possible to do duno tuning through usb to usb plug.

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HaltechMatthew
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Re: Signal ground has continuity with Chassis ground when ECU plugged in.

Postby HaltechMatthew » Thu Oct 18, 2018 1:40 pm

You have something very certainly screwed up if you can melt the USB cable just by trying to going online. I cant even think how it is possible!


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