Code P1780 intermittent no start issue?

Hi,

Your description does sound like a crankshaft position sensor, but you already replaced that. Here is what I need you to do.

When this happens, we need to determine if we lost spark or fuel to the engine. Try this. See if the engine will start if you use starting fluid. If it does and then stalls, we know its fuel related. If there is no change, I need you to check for an ignition spark.

Here is a link that explains how that is done:

https://www.2carpros.com/articles/how-to-check-for-ignition-spark

Try this and let me know what you find.

Take care,

Joe

I'll do the tests asap. One thing I forgot to add earlier; I had some questions about the fuel pump relay, so I swapped it with the wiper relay. The car started fine. I let it idle a bit and shut it off. I then decided to gas it up, car started fine, I went for gas, after filling up, engine would not start. The engine at this point was fully warmed up. Got pushed to the side (did some shopping) about 1/2 hour. Later I was able to start the car and drive home. Looks like the relay is not the problem, since the swap gives the same result.

Hi,

When you switched the relays, was the engine not starting prior to switching them and then starting after the switch? If that is the case, remove the relay and confirm the connectors in the box are in good condition, not corroded or pushed inward.

Let me know.

Joe

When I switched the relays, the car had been sitting overnight. It almost always starts right up, first try when it sits overnight. The starting problem usually happens after the car has been driven, shut down and then attempted to re-start. When I switched the relays, there was no change to the way the car started, or the way it failed to start. The relay connectors are in good condition, and I've been spraying them with "Deoxit" which is the best contact cleaner I've found.

The starting problem has been going on for several months. I can always get the car started, sometimes it takes several tries, but sometimes it takes a long wait before I'll be able to start (the problem seems to be temperature related but not always).

When it cranks but doesn't start does your gas gauge ever read empty even though you know you have plenty of gas?

I have not seen it read empty. But, while I haven't seen it, it is possible that I didn't notice since I wasn't looking for the fuel level while cranking. I will make sure to check the gauge next time the car won't start.

Yes. just turning the key on if it reads empty what i am getting at here is those cars have a high rate of failed body control modules. Causing lots of different issues on of which is intermittent crank no start and a lot of the time when that happens the fuel gauge will read empty. Have seen that lots of times. They can be sent out and repaired and that way you won't have to have the new one programed. Let me know what you see when it doesn't start. The engine control module fails on those also and cause a crank no start. But when that happens I haven't seen them start again.

Also, when it doesn't start see if anything else doesn't work as well power door lock keyless entry can't shift out of park dome lamp etc.

I am quite certain that everything observable remains functioning during the times the engine won't start. I have sometimes shifted from Park to Neutral to see if that makes a difference, it doesn't, but Park is not locked. I also have operated the power windows as well as the power door locks (via the button on the door) at times of no start. I don't have or use a keyless remote (my wife might have the only one). The "dome" light always remains on with the door open (I often open the driver's door in a no start situation). There are a couple of routines I found on the Net that were posted as a possible help to start which I try and sometimes they seem to work, but often they don't.

Drove to work yesterday, car started fine in AM, but after work it wouldn't start. I sprayed some carb cleaner into the intake manifold, but that didn't help (not a cough). Looks like spark might be the issue. I did get it to start a few minutes later. To check spark, I'll have to remove one set of intake runners, and remove the coil pack. Should I ground 2 of the spark plug connectors while I test the third for spark?

Would it help if I post all the reading items from my scanner? I only posted the main code.

Before get too crazy down the spark rabbit hole when it doesn't start can you link your scanner to It?

Yes, I'll take the scanner with me so it's available.

Is it possible for the car's computer to get corrupted, and if so, is it possible to reset it? A while back, I bought a "gas saver" gizmo, knowing it might not work, but I wanted to see if I could learn anything (it plugged into the OBD connector). Seems like the starting problem started after that. I only ran the gizmo for 3 tanks of gas, then I took it out to plug my scanner in (because of the starting problem). That's when the P1780 code showed up.

I doubt the computer is corrupt it sounds like something is getting hot failing and then cooling down.Your for sure the gas gauge works when it doesn't start?Also let's see if you can talk to the computer when it doesn't start with your code reader? Also, happy Thanksgiving to you and your family.

Thanks, and happy Thanksgiving to the crew at 2CarPros!

You guys were right! And I'm finally making progress. I connected my scanner, turned key on and noted that the fuel gauge was on "E". Engine would not start, key off, key on, now fuel gauge "F", scanner connected and displayed some codes, then lost connection. I started the engine and scanner tried to connect but failed. Key off, key on, fuel gauge "E". I repeated this procedure several times, and "E" equals no start/"F" equals start. (Duh, don't tell me the ECM checks the gas gauge to see if it should bother to start or not, LOL). I pulled the codes from the scanner memory: #1) P0102 (this is new and probably related to my use of carb cleaner to try to start -- I did shoot the cleaner downstream of the MAF sensor, but I guess it didn't like the smell, lol)., #2) P1780, #3) P0160, #4) U2105.

Okay, from what you told me from the gas gauge reading empty I remember not being able to link to the ECM as well. So, what i am going to say is you have an issue with your body control module every time I have seen the fuel gauge read empty.Your best bet is to have it repaired will save you the money on buying a new one and having it programmed.Its mounted to the top of the inside pocket of your glove box will get you replacement instructions soon Super easy to do.Is this your primary car?Because it will be down while your body control module is being repaired.

Great! this has been a real mystery. My Wife has a car, so I'll be able to get around.

https://www.g7computers.com/pages/how-does-this-work

That's the link to the repair service I had a friend send than a 2002 Saturn sc2 body control module that didn't start that had a bad BCM.He loved their services they did a good job. Its been atleast 3 years and the module still works great.I don't remember if he had to relearn the pass lock sensor or not.

Please let us know your progress and all that they will even test the module for you and all that.

Thanks, I'll get to work on this.

You're welcome.

My BCM was repaired by G7 computers and is in transit to me. G7 emailed me the following note:

"The computer you sent here has been repaired. There was a hardware failure on the board. Usually when the computer fails, so does another part on the vehicle, and if all the damaged parts on the vehicle are not replaced at the same time, then the original problem may still exist, or even cause damage again to the computer and/ or vehicle. Anything electrically related to the symptoms with the vehicle should be checked. It could not be determined if the fault was a result of a short circuit in the vehicle or a manufacturer's defect because the vehicle was not here for inspection."

My next question is going to be: "How do I check for anything that could have caused damage to the BCM?" Hopefully, G7 will include more info with the BCM....

Hi,

Since there was an issue with a no-start condition, were you able to determine if it was an ignition or fuel-related issue?

What they are telling you, in my mind, is a way to protect themselves. But if you recall anything electrical that was causing issues, let me know and we can check some things.

Joe

I tried spraying carburetor cleaner into the intake when it would not start, engine should have started, it did not even cough. Looks to me like the problem was no spark, but only if the gas gauge read empty, if it read correctly, it always started. I missed this at first but was asked about it 2 or 3 times and finally I got it right.

All the Saturn L series I have seen that don't start when the gas gauge is inoperative was a bad body control module. I have seen tons of them. It's really common for them to go bad I lost count with all the ones I replaced all the years I worked at the Saturn dealer.

I have never tested for spark when I ran I to that situation I have also seen the engine control modules go bad but way far less common and when they did it was a tow in.I could never get them to start even to drive them into my shop.

After the "no-start" issue began, I checked for codes: #1 was P1780 PNP SW, I replaced that, but it didn't help. However, might that code have been set when the BCM failed? Is there anything I should be looking for? Otherwise, when my BCM returns, I know of nothing to do except put it in and try it. But I don't want to fry it again if there is still some issue that caused it to fail.

Oh, one other thing that I was going to ask about after the no-start was fixed has to do with the trans. Possibly this is also related to the BCM. I included this in my report to G7 when I sent the BCM. The trans is auto and sometimes (randomly) it shifts rough. I have read online that this is due to the line pressure solenoid failing or not getting voltage to actuate properly. This problem precedes the no-start issue but has some similarities. Usually when the car was first started in the AM, the trans would shift smoothly. Sometimes, after a stop (gas, shopping, etc.) on re-start, the trans would shift rough. Note that if the engine started and the trans shifted smooth, it would always continue to shift smooth as long as the engine was not shut down. Likewise, if the engine started and the trans shifted rough, it would continue to shift rough as long as the engine was not shut down. Start-up determined if the trans shifted smooth or rough.

What I have seen when the line pressure solenoid is going bad on those you get a hard shift and when you cycle the key the hard shift goes away.When the solenoid gets bad enough it will set a code p1811 basically transmission adaptives can't compensate for the shifting issue being caused by the failing line pressure actuator.When the transmission can't control the line pressure it will going into a fail safe mode.Which it shifts the transmission at full line pressure to help keep the clutches in the transmission from slipping and burning.Down side is if it's operated over too long of a period like that it will destroy the transmission.I have seen a ton of bad line pressure solenoids go bad a few of the other solenoids go bad.But those were seldom compared to the line pressure solenoid I don't see the transmission issue being related to the bcm at all.I have seen a bad bcm not let the car shift out of park and also cycle the transmission.Shifter release solenoid off and on over and over all by itself for no reason whatsoever.

The BCMs on those just fail for all different reasons and cause an array of different symptoms and codes to set.The most common symptoms is that no start and fuel gauge inoperative.

I received the BCM from G7 yesterday evening and today I installed it. Went to start the engine, fuel gauge read properly, and the engine started. I let it idle, then shut it off to load the car for work, when I tried to re-start, the fuel gauge read empty, and the engine would not start. I tried several times -- no start. While there is an outside chance that the BCM was not the problem (since the car was previously most likely to start after sitting overnight) I suspect G7 was right in warning me to look for shorts, etc. that could have caused the BCM to fail. Looks like I damaged the repaired BCM.

At this point I'll have to either find the short(s), re-repair the BCM or junk the car. To find the short I'll need a correct wiring diagram and what values I should test for on the pins of the connectors, any ideas will be much appreciated. I also plan to tell G7 what happened and see if they can make suggestions.

Did G7 say they found a problem with the bcn when they repaired it?I have never seen a short on one of those cars cause the bcm to fail and cause the fuel gauge to intermittently fail not start and have the fuel gauge inoperative.

Yes, G7 included this note with the returned BCM: "The computer you sent here has been repaired. There was a hardware failure on the board. Usually when the computer fails, so does another part on the vehicle, and if all the damaged parts on the vehicle are not replaced at the same time, then the original problem may still exist, or even cause damage again to the computer and/ or vehicle. Anything electrically related to the symptoms with the vehicle should be checked. It could not be determined if the fault was a result of a short circuit in the vehicle or a manufacturer's defect because the vehicle was not here for inspection."

Hi,

I noticed Saturntech hasn't contacted you for a couple of days. Have you been able to make any progress? I stepped back because he is excellent with Saturn vehicles.

Let us know.

Joe

Hi Joe,

I think what I'll have to do is find an accurate wiring diagram with the values that I should get if I check the pins of the connectors to the BCM. Otherwise, how can I possibly check for any malfunction in the system that the BCM is connected to? Do you know any way to find such a diagram?

Hi,

Yep, I understand. What we can try is this. First, I attached the connectors for the BCM pinout below. Next to the pin number, you will find what each wire is for.

Next, I attached the wiring schematic for the BCM. I had to cut it in half to make it readable for you.

Let's try it this way. Let me know the wires/connectors/pins in which you have an interest. I will try to determine what you should find at those wires.

I wish I had an easier answer. I understand what you are asking for, I've never seen one in a manual. There is always a focus on one or more specific circuits that are checked. They don't have a schematic covering all wires and their values. It would be a good idea, but that has never shown up in my manuals.

Let me know your thoughts. Let me know if you feel this will help.

Take care,

Joe

See pics below.

Hi Joe,

You guys are incredibly helpful and much appreciated! I will get to this and report back asap. I have looked over the pics, but nothing is obvious related to my problem. I plan to check with G7 next to see if they can shed some light on this (such as what component(s) they fixed and any suggestions they might have. BTW, I hope you got paid a commission for referring me to G7, you deserve it.