Adam96Z

Did you check out all the vacuum lines for leaks? A small vacuum leak can cause this problem, if the car is that old, I bet some of the lines and elbows are dry rotted.

Also, I'm not sure if you already did this and I don't want to re-read the thread. Did you put a meter on the TPS to check for a smooth 0-5v from 0 to 100% throttle.

Also a pin on the electrical plug that is partially pushed through on the wiring harness can cause intermittent problems. I have a GTP that had the same problems and it ended up being a couple pins that had pushed out of their sockets from being removed every week or two due to tear downs for drag racing.

Guest47904

Aside from checking the 5 volts on the MAP and the TPS. I also remembered something about the alternator.

First, check that the same codes return after clearing them. If different codes return each time you reset them then it's time to check the alternator diodes for leakage.

First see if the alternator is charging properly by checking the voltage across the battery with a DVM set to DC. You should always see at least 14 volts while the engine is running. If not check the battery first. A bad battery may by sucking in everything you can throw at it. If that's ok now set the meter to AC and measure from the output post of the alternator to the negative terminal of the battery. With the meter set to AC you never want to see more than 0.03 VAC. If it is higher than that, the diodes internal to the alternator are leaking and allowing AC on the DC supply line.

This can have the effect of screwing with the PCM. But that is not likely if the same error codes keep coming back up. Don't forget to check the gray wire of the TPS and MAP for 5 volts.

Daniel6718

ill check when i get to work in a bit a report back...i initially cleared the codes when this started these are the same ones from before...its weird because i havent seen any problem from any of those sensors on my "scanner" as in they have always communicated with the pcm and my scanner.

the battery in this car isnt that great, it is hard to start. i will be looking into that, plus it has a big stereo, but like i said before i disconnected itill check those wires and doing some pulling and moving the harness and see if i can make it intermittent if its there

i did check it before and running it has about 14.2 volts with everything off but one fan

no vac leaks the iac is opening causing this...i checked them with a can of carb cleaner, and i also felt over the oil filler neck doesnt appear to be leaking into the lifter valley either

Daniel6718

map and tps both have rock steady 4.92 volts a them....they both also have a steady ground it is .070ohms between it and ground all the time
pcm has steady 4.92 volts


alternator on ac to the battery neg terminal has .068-.070

battery with the car off has 12.7 volts steady

Daniel6718

now i have a code 16...loss of low res signal...???

Daniel6718

next step? try another opti? the customer today told me this started after he put on a new opti plugs and wires...i checkd the plugs and wires they are good...new plugs and wires ohmed fine

Guest47904

The diodes are bad. If you don't believe me, take the unit to a reputable shop. Not AZ and ask them to test it. Check another vehicle that is running fine for it's readings. Do an internet search to back it up.

Any amount of AC on the DC supply line can have strange bad effects.

May not be your only problem but it is A problem. I would start with the things you KNOW are A problem before you start guessing.

Daniel6718

kool and i agree...always fix known problems and go from there...ive got a good alternator and starter place to get one built at...ill get that done. hopefully this fixes me up

i should have gone back and read i thought u said 3 volts ac...im sorry guys

Daniel6718

ok i took the alternator to a shop they told me it was fine...i specifically told them tocheck the diode...i came back and swapped it with another lt1 and same readings...same problem

i removed the belt and it idles much better but still surges, say once every 2 minutes...normal it is 6 a minute

Guest47904

This can be the whole problem. But there are a few ways you can get a 16 that is NOT the fault of the opti. WIRING problems.

You need to look at the signal on both ends of the wiring with a scope to see what comes out of the opti and what gets to the PCM.

This would also account for your surging.

However, an active code 16 would shut off the injectors. So if it's running, the problem is intermittent and that is almost always wiring.

Daniel6718

i ohmed the low res wire the whole time and it was perfect no resistance...

also according to alldata between the low res signal wire and grouns should be 3 volts running, i have 1.7?

posible inside the opti problem?

and i found the pcm ground wire broken by the back pf the passenger head just hanging loose...i ohmed it and its grounded anyways but i fixed it no help there

Guest47904

I don't know what "whole time" means but you CAN NOT ohm a wire that has a signal on it. Nor can you ohm a wire that is hooked to something on both ends. You should always unhook one end.

The other point is both the hi and low res signals go between 0 and 5 volts. This would give a square wave while the engine is running. What ALLDATA is doing by having you measure the square wave while the engine is running is finding the RMS value of the wave. Interesting way to measure a square wave with a meter BUT. Most meters you purchase are NOT true RMS type. I do believe in order for your meter to measure a wave form, it has to be set for AC not DC.

I mentioned some posts ago how to measure it with a meter AT THE PCM while someone rotates the engine around with a breaker bar. You should check the opti end if the PCM end is not what you expect it to be.

Next, you can't rely on engine grounds for a signal that has it's own reference. Such as the hi and low res. It should always be measured to reference, not engine grounds.

As far as the low res signal and a DTC16, usually it's the wiring causing a problem. If you eliminate the wiring DEFINITELY, then there is only one choice left. However before you give up on the wiring, I would tighten up all the female connector pins in the chain from the opti to the PCM.

Last point to be made today. ALL the ground points should be checked particularly since you found one disconnected. BUT we don't know B body grounds on this forum.

Daniel6718

i ohmed it while the car was running and surging...and completely un connected on both ends...while moving the harness around tugging and pulling...

when i checked the opti i checked it at the connector on the side of the intake...ill try it at the pcm and check, and i know to check it with its ref.

ill go over both female connectors if that doesnt do it i dont know what else in the wiring could be it.

Guest47904

WTH you talking about?????? The engine won't run with the low res signal disconnected. You loose the firing pulse to the coil and the PCM shuts off the injectors.

Are we talking about the same thing???????? If you thought you were checking the low res wire. I have news for you.

Daniel6718

i stuck a needle in it while it was running and surging...and i disconnected it and checked it cold and hot...no differance...the connection was perfect...0.00 ohms resistance during all checks