Tech 2 question for those that have them

I just got a clone Tech 2 and did a first test on the 96 RMW All the screens and stuff are cumbersome but no big deal, but I did run into an unexpected issue with it.

I was under the impression from things I read and posts people put up, that you should be able to get the Tech 2 up and running and on the engine data screen and then start the engine and continue to watch the parameters. I will be on the engine 1 parameters and seeing all the data with the key on, but when I turn the key and start the engine the Tech 2 blanks and comes back with communication error. It stays locked up saying no communication when I shut the engine off with key on. It won't reconnect unless I shut Tech 2 off with it's power button and start over. If I start the engine before turning on the Tech 2 in the first place it reads just like it should after I go through the whole setup so I miss all the afterstart data.

The Tech 2 is powered only through DTC port as the instructions say not to use the separate power cord to the unit or connector. It looks to me like the DTC is interrupted at start like the other things in the car do and that is messing up the Tech 2. If the power source was uninterrupted direct from battery it might be fine, but they say not to so a bit scared to do that.

Can anybody shine some light on this?

On a 1996 RMW, the Data Link Connector is powered by the 60A Fuse 11 (Body 2) which is hot at all times.

I'm guessing that there's a voltage dip when the starter engages that the fake Tech 2 isn't able to ride through and maintain power.

Maybe try a 2nd car/battery connected with jumper cables or a jumper pack of some sort to keep the voltage up during cranking.

FWIW, the cigar lighter is connected using the same wire as the data link connector, so if you can inject some power there, it may be easier/more effective.

Fix Until Broke wrote:

On a 1996 RMW, the Data Link Connector is powered by the 60A Fuse 11 (Body 2) which is hot at all times.

I'm guessing that there's a voltage dip when the starter engages that the fake Tech 2 isn't able to ride through and maintain power.

Maybe try a 2nd car/battery connected with jumper cables or a jumper pack of some sort to keep the voltage up during cranking.

FWIW, the cigar lighter is connected using the same wire as the data link connector, so if you can inject some power there, it may be easier/more effective.

Thanks, that what I needed to know and didn't have the time to go through the hard to follow format of the FSM. That is how our 2007 Exrpess van is wired also and the RV upfitters always mess it up by tapping into the lighter line. With the DTC not interrupted all that is left is the voltage drop.

The Tech 2 warning about not powering it off with separate power sources is probably to prevent back feeding through the DTC connector so that also makes sense. The lighter circuit might do the same thing and run too high a current backwards to the engine, but it would save the Tech 2 a bit I think.

Perhaps the better thing to do would be too disconnect the DTC power wire or pin between the DTC plug and the Tech 2, leaving the DTC as is and making the Tech 2 to be powered off the remote power supply or a small battery that rides along like it would be on a OBD1.

I could also try putting my 40 amp leftover, settable, RV charger on the battery to see if that is enough. I only had a little 7 amp CTEK on it in this test.

If you're concerned about running current backwards to the engine (I wouldn't be...), just pull CIG/DLC Fuse 28 (20A) and power the Tech 2 through the cigar lighter with an external power source. Those are the only two things on that circuit, so with the fuse removed, there's nowhere else for current to go.

Fix Until Broke wrote:

If you're concerned about running current backwards to the engine (I wouldn't be...), just pull CIG/DLC Fuse 28 (20A) and power the Tech 2 through the cigar lighter with an external power source.  Those are the only two things on that circuit, so with the fuse removed, there's nowhere else for current to go.

Good idea, thanks. Do you know off the top of your head which pin of the DTC is power?

I had the same problem when I got mine a couple years back. I remember reading on some forum…..that inside the Tech 2 there’s a ‘power supply chip thingy’ soldered to the motherboard, that runs everything. On an authentic tech2, that ‘chip thingy’
Can still deliver smooth, uninterrupted power to run everything it’s supposed to….even when the input voltage (supplied via the DLC) drops to 10.5 volts while cranking. With our counterfeit tech2, it’s made with a cheaper ‘chip’ that can NOT keep the tool powered up while cranking….so after you start the car, you gotta start all over. If I can find the article, I’ll post it here. The author’s solution was to buy a high quality chip for $25-30, de-solder the cheap one off the motherboard, and install the better one. Because I use phrases like ‘chip thingy’, you can tell I’m probably not slick enough to make that upgrade. So I took about the Candi module, cut the wire that receives B+ from the DLC, and wired it to a toggle switch. So if I’m tryin to use the tech2 to monitor something while cranking, I flick that switch off, and power the tool using a separate jumpbox. Powering the tool using the cigerette lighter won’t work, because voltage drops everywhere while cranking.

Found a video with a fix.

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You use an extension cable with a power on/off switch for the power.  

If you are going to be starting the car, you hook up the AC adapter downstream of the switch into the connector or unit, and have the switch in the off position.  It will then power off the AC connector all the time and not drop out on starts.

You could also use a second battery and the alligator clip power cord is you need to drive it that way.

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Pin 16 is power

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Nice illustration, thanks. Did you get a chance to look the video of the cord switch? Sure looks like the easy way to go as long as you remember to turn it off if you want to use the port power so you don't have both running at the same time. I will probably just tape it off as a reminder to just remove it.

Are you familiar with ECM-Pro Scan software paired with the Jet DTS scanner to be used for data logging with a laptop?

The cord switch looks like a pretty simple solution - didn't know things like that existed so thanks for sharing.

I'm not familiar with any of the software/hardware you mentioned, sorry.