LS2 swap-throwing codes P1682 P1516 P2101

[Chris 68]

Trying to get this project on the road by Monday and having some issues.

I can get everything up and running, however I'll keep getting the P1682 code "ignition 1 switch circuit 2" and nearly every time I'll get the p1516 and sometimes p2101 codes as well, with a total loss of throttle body response and a really rough idle.

I can clear the throttle body codes (usually) and regain TB, but it will come back when I start the car again. Most recently when I had the engine up to temp to get the cooling fans on, the signal for the fans was erratic and going on and off like it had a weak connection. (Fans are connected to infinity box and there is no issue there).



My biggest concern is the P1682 as the other codes are intermittent. (I have a feeling they are related to P1682). The LS2 T56 came out of a GTO, along with the E40 ECU, pedal, throttle body, etc.

the harness was done by wait4me performance a while back. I have an infinity box 3 cell system. I don't know the pin outs but I know I have a large pink wire and a smaller pink wire that have their own relays and are switched on by the infinity box system. The starter is directly controlled from the infinity power cell. I have a constant 12 volts to the ECU thru an orange wire if I remember correctly.


I've searched and searched but still scratching my head. If any body has any suggestions on where to start I'd greatly appreciate it!

[Chris 68]

More information: I'm reading a voltage difference on the IGN1 of about .03 volts less than the PCM constant wire. I'm also seeing a couple ohms of resistance to ground when referencing IGN1. Not sure what this means though?

[Razzor67]

Check out your ignition switch. That code ties directly to a fault in the switch or wiring to it.

[Chris 68]

Check out your ignition switch. That code ties directly to a fault in the switch or wiring to it.

Thanks for the reply Razzor. My switch is OK, I'm seeing voltage differences after the switch.

[dhutton]

.03 volts should not make any difference. Is everything properly grounded?

Don

[Chris 68]

.03 volts should not make any difference. Is everything properly grounded?

Don

That's what I was thinking. I think I'm ok with grounds, all the stock GM points on the engine, engine to frame, engine to body, frame to body, transmission to frame, and since I have a trunk mounted battery, body to battery (I believe 2 points) and I ran a heavy (1/0?) guage wire directly from battery negative to the engine block.

I increased the wire guage thickness for the IGN1 to 8 gauge and was able to turn the ignition on and off several times with. I codes. Started it up and let it run for about 15 minutes, revved it up a little, TB was good. Then turn it off and try to turn it over again, get the rough idle, 1682, 1516 and 2101 codes?

[Artisan Motoworks Club]

little trick for a easy way to check a bad ground.. take a test light and connect the gator clip on battery ground. Use the tip of the test light and touch ground that you think are good. Test light will light up when you touch a bad ground.

[Chris 68]

little trick for a easy way to check a bad ground.. take a test light and connect the gator clip on battery ground. Use the tip of the test light and touch ground that you think are good. Test light will light up when you touch a bad ground.

Thanks for the tip! I'll have to start checking grounds while I'm at it.

[DT69Cam]

Alternator good ?

[Chris 68]

Alternator good ?

To my knowledge it is, its brand new 180 amp alternator. I'll go have it tested though.

Update: back from getting it tested, alternator is good

[DT69Cam]

Also The "ignition switch" theory as per DTC 1682 doesn't apply to our old cars IMHO. What car is this LS2 in now ??

[Chris 68]

Also The "ignition switch" theory as per DTC 1682 doesn't apply to our old cars IMHO. What car is this LS2 in now ??

68 Camaro but I'm not using a key, push button directly to infinity box system

[DT69Cam]

68 Camaro but I'm not using a key, push button directly to infinity box system

Infinity alone ?? I definitely would check your connections then.

[Chris 68]

Infinity alone ?? I definitely would check your connections then.

Well because of the amps, I have the 12volt switched power for the motor on a couple of relays and they are switched on by the ignition output on the infinity box side. The relays are working and I seems to be getting proper voltage. I've even bypassed the relays to make sure and used some jumper cables to add more grounds from the engine to the battery but I'm still getting these codes. But it's only after I shut off the motor after it has been running. I can cycle the ignition on and off as much as I want. I can run the motor as long as I want with full throttle response. But once I turn off the motor and then turn the i groom on again, I get a CEL.

[DT69Cam]

Well because of the amps, I have the 12volt switched power for the motor on a couple of relays and they are switched on by the ignition output on the infinity box side. The relays are working and I seems to be getting proper voltage. I've even bypassed the relays to make sure and used some jumper cables to add more grounds from the engine to the battery but I'm still getting these codes. But it's only after I shut off the motor after it has been running. I can cycle the ignition on and off as much as I want. I can run the motor as long as I want with full throttle response. But once I turn off the motor and then turn the i groom on again, I get a CEL.

That is strange man.

[dhutton]

I'm going to guess some kind of power sequencing or glitch issue on shutdown. I'm not really following exactly what you have done but this is my suspicion. Sounds like something is latching up due to improper power sequencing.

Maybe post up a schematic of what you have.

Don

[Chris 68]

I'm going to guess some kind of power sequencing or glitch issue on shutdown. I'm not really following exactly what you have done but this is my suspicion. Sounds like something is latching up due to improper power sequencing.

Maybe post up a schematic of what you have.

Don

You were close, I believe I just found the culprit! Took apart the harness going to the computer and found the smaller ignition 1 wire was tapped into the constant 12 volt going to the ECM. Now it makes sense the code (p1682) would hit only when the ignition was off.

Now I have one last question for you guys: can I just tap the smaller ingnition wire (pin 19 C1) into the larger one (pin 14)? Or would it be best to put a separate relay in for that?

[Chris 68]

Splicing my pin 19 wire into the keyed 12 volts for pin 14 seemed to do the trick. No codes!

Thank you everyone for your help!

[Chris Edwards]

Splicing my pin 19 wire into the keyed 12 volts for pin 14 seemed to do the trick. No codes!

Thank you everyone for your help!

Did this fix the problem long term?