replacing LM1815 chip

[njorge0319]

ok so i have no VR trigger signal input at all, tried to do record trigger logs and i recieve some bytes when i crank the engine but other than that i get no input at all.

the car used to run great, i had been doing alot of work on the car and forgot to reconnect one ground wire from pin 26 to the main sensor ground junction in the harness near the ecu. its obviously reconnected now but i think i may have damaged the lm1815 chip. everyone i talked to had said i probably burned the p259 chip but my fans and fuel pump run off those channels and are working fine. i even disconnected leg 21 to see what would happen and still no crank input.

i ordered a lm1815 chip and should have it soon. in the meantime is there any tests i can do to verify that is whats wrong?

and if it is and has to be replaced whats the best way of doing it? its so damn small. i heard something about using a heat gun with tinfoil and pliers to remove the old one?? any suggestions?

other than that is there anything else i should be looking at for no vr trigg input??

[GintsK]

Damaged P259 chip causes +5V drop for P259 and both LM1815. And it does not cause LM1815 failure.

Supply voltage is easy to measure.
I never seen fried LM1815 so far. From almost two hundreds users. But you knew...

For replacing - search for Chip Quick video. They offer nice kit for desoldering. But it also can be done in same manner using usual solder alloy and very hot soldering iron.
Heat gun is bit dangerous - it easily desolder everything around. You have to make good mask. I think you can find some helpful youtube videos too.

Tests. You have to verify is everything is soldered right. Most handy test is triggerlog anyway. Output pulse from LM1815 is very short. And only alternative to check it is o-scope.

Gints

[njorge0319]

Thanks.
My p259 is good. I have 5v at leg 8 on the lm1815 with key on. drops down to 0v when i crank it. not sure what other legs i can check. the circuit siagram on that chip i confusing to me. Having the lm1815 be bad is the only thing left I can think of really. My wiring and sensor are good but I'm not getting trigger input when I try to do record trigger logs. If its something else I'm not sure where to look and I may need to send the ecu in to be checked n repaired. I should have those new lm1815 chips today or tomorrow so Im going to replace it and see what happens

[GintsK]

Thanks.
My p259 is good. I have 5v at leg 8 on the lm1815 with key on. drops down to 0v when i crank it. not sure what other legs i can check. the circuit siagram on that chip i confusing to me. Having the lm1815 be bad is the only thing left I can think of really. My wiring and sensor are good but I'm not getting trigger input when I try to do record trigger logs. If its something else I'm not sure where to look and I may need to send the ecu in to be checked n repaired. I should have those new lm1815 chips today or tomorrow so Im going to replace it and see what happens

Did your ECU have supply during cranking!?

[njorge0319]

You talking about the main power supply at pin 25 on ec36? It should. I can check voltage there while cranking when I get to the car later today

I'm talking leg 8 on the lm1815. 5v with the key on then when I cranked it that dropped down to 0v until I let go of the key then it went back to 5v

[njorge0319]

Yeah pin 8, thats the pin I was told to check the voltage at

[GintsK]

It depends _directly_ from supply voltage.

[njorge0319]

So I replaced the lm1815. Still nothing. Just tried setting my trigger type to "coil type" and I taped a wire to my vr signal wire and tapped it to 12v to see if I would get a blip in the trigger log. I didn't see anything but I did hear an injector fire.

Anyways I thought i'd add this, I don't have an alternator on the engine right now. Do you think that has anything to do with my problem? could i be loosing too much battery voltage to the starter and hitting ecu reset while cranking?

ive been waiting for my alternator to show up from INA, should be here any day now.

[Kamuto]

So I replaced the lm1815. Still nothing. Just tried setting my trigger type to "coil type" and I taped a wire to my vr signal wire and tapped it to 12v to see if I would get a blip in the trigger log. I didn't see anything but I did hear an injector fire.

Anyways I thought i'd add this, I don't have an alternator on the engine right now. Do you think that has anything to do with my problem? could i be loosing too much battery voltage to the starter and hitting ecu reset while cranking?

ive been waiting for my alternator to show up from INA, should be here any day now.

alternator don't work on cranking. check 12v supply to ecu when cranking as Gints said.

[njorge0319]

Wow I think that may have been it! The wire I had switching my relay had 12v key on and when I turned the key to crank it it dropped down to almost 0v. I didn't have time to check more than that this morning. I'll swap to a different wire when I got home today, hopefully that will fix everything!

[njorge0319]

Thanks for the help guys! I can't believe I overlooked that.glad that's all it was though. Got the car fired up today and its running great!

[Kamuto]

Thanks for the help guys! I can't believe I overlooked that.glad that's all it was though. Got the car fired up today and its running great!