Good Morning all, I'm hoping someone can help me out. I went to go to work this morning and my '97 didn't want to start. I finally got it started but threw some codes and said reduced power and traction control warning. Anyway, I did the diagnostics check and it gave me 3 current codes. 10 PCM P0161 & P1518 and 28 TCS U1255. I cleared the codes and the car started fine afterwards. I shut it off and tried restart and now it's doing the same thing but now has a 10 PCM No Comm message when it's doing diagnostics. Any idea where to start? car ran fine 2 days ago, is it just jealous that I as riding the motorcycle instead so it's teaching me a lesson? Any help would be appreciated. Thanks in advance.

 

If you have a PCM "No Comm" I'd concentrate on that first...the P1518 and U1255 are most likely related to the no comm. The P0161 is a heater circuit issue with your bank 2 sensor 2. Do you have a DVOM, know how to use it and are able to get to the PCM to check a few power and grounds ????

 

On a side note, maybe related and maybe not, we did have a pretty good storm come through last night, lot of rain and wind. Any chance something got wet that shouldn't have? I just tried to start the car again and it will start but with reduced power if I reset the error codes first. If I turn it off and restart again, it just cranks and doesn't fire again. Gauges all work as they should except the tach doesn't move and it took a little bit for the fuel gauge to go up. I do have a DVOM, I don' have tons of experience with it, haven't tried to get to the PCM. If i remember correctly it's inside/behind drivers tire footwell?

 

First thing I ALWAYS do in a diagnosis is check the condition of the battery...if you can take it to your local auto parts store they can load test it...now you said the Tach doesn't move...that's a quick test for me when I see a crank no start...it may be a bad crank sensor...you will have no spark AND no injector pulse...if it is still cranking but not starting just pull a plug wire off a coil pack and hold the plug wire about a half inch away from the coil pack...if NO spark seen and to verify crank sensor bad you need to check injector pulse...pull the connecter off an easy injector to access...take a 12 volt test light connected to battery POSITIVE...touch the tip of the test light to the wire that is NOT pink....have some one crank the engine and if you have injector pulse the test light will blink as the engine turns over...if you had a lot of rain remove the access panel at the passengers side footwell where the BCM and fusebox are located...see if it is damp in that area...the BCM doesn't like to get wet !!...the PCM is located behind the passenger side front quarter panel so the front tire and the plastic cover at the rear of the wheel well needs to be removed...if you don't feel confident with this I would take the car to a good diagnostic shop in your area !!

 

I've checked the passenger footwell already and all is good there. I didn't think about the crank sensor, I had that happen to another car of mine, similar symptoms. I'll look into it when I get some more time today. Thanks for all the suggestions so far. Much appreciated.

 

Update: i turned the key on, pulled fuse # 16 & #23 from the fuse panel in front of the battery, turned key off, put fuses back in and the car fired right up, all the codes were gone and no comm error. I turned the car off, and now I'm getting 3 PCM codes but didn't have a chance to write them down yet. All the gauges are working except for the tach. It was moving at all when it was running but when you first turn the key on it does go up and back down with everything else. I feel like I'm getting close to narrowing something down but what exactly am I narrowing down? I don't know yet. Could it be something with a ground somewhere? Could it be my PCM is taking a crap altogether? I checked the battery and I'm at 12.0v just sitting in there, no load, nothing on.

 

See what 3 codes you have ??…did you check the battery voltage at the battery terminals ??…if you want to check proper battery voltage check it at the battery…if you read it at the DIC it reads about .4 to .5 volts lower than actual battery voltage…before condemning a bad PCM you should check it’s power and grounds first !!

 

Sorry Guys, I was painting a motorcycle all day Sunday, working all day Monday so I hadn't had a whole lot of time to mess with anything.
1.) Checked the battery with a meter and not just the cars display. Haven't been able to check it while cranking the car over.
2.) I've got 2 current PCM codes. 0654 and 1518. It did show a history of 0102, 1571, 0654
3.) I clear the codes and the car starts right up. I haven't tried driving it yet but I've let it idle for about 10min and no issues. If I shut it off and try to restart it won't. With that being said, I don't think it's a battery issue or a PCM issue. It seems like a sensor issue somewhere and I'm leaning towards the Crank sensor. If it was a PCM issue with it going bad I don't think clearing the codes would matter, it would seem like it would be a constant problem. What do I know? I'm just a dumb crime scene/trauma cleaning guy. Any thoughts (on the car, not my mental competence)?

 

PO335 is a crank sensor. I believe that PO336 is, too. You're not getting these codes, so why suspect a crank sensor? C5Diag asked about battery voltage. You checked it, but didn't mention what reading you got!! You're getting a PO654 H AND C! It is obviously an issue. I don't remember off hand what the PO654 code is for. But it's a good place to start. Best of luck to you.

 

Battery was at 12.0V without the car on or running. I haven't had a chance to check while cranking or running yet. I've gone out and the car has started up just fine for the last 2 days now in the driveway. I haven't driven it yet to see if any problems come up while it's running. No codes, everything is working fine. The keyfob stopped working with the car so I re-synced it and all is well with it now to. I'll look up the P0654 code. Thanks for everyone's input so far.

 

P0654 = Engine Speed Output Circuit, PCM, IPC Module, HVAC Systems Automatic.

 

Battery is at 13.76 running. I drove it around the neighborhood, slight hesitation taking off but goes as normal after that. RPM's dropped down to about 300 when I pulled in the driveway and it died while in drive and my foot on the brake. Started right up, no codes. I do hear what I think is the fuel pump whine which I don't remember hearing before but it's now into the mid 90's outside and I may have heightened awareness, it could've been doing it all along.

 

Add more to the sage. No codes showing, car starts but after about 4 seconds of cranking, idles fine but as soon as you turn the HVAC on the RPM's kick up to 1,500 and become erratic and then drop back down, car starts to run rough. I put it in gear and the RPM's kick up slightly and then drop down to 300 or so, if I kick the HVAC off quick enough it won't die but if I don't then the car dies out. No longer think the crank sensor, the fuel pump is priming and running as it should it seems. Any guesses?

 

At 12.0 volts your battery is basically “dead” !!…I would highly recommend taking the battery to get load tested…I do a “starting and charging” system test on EVERY Corvette I look at…copy of test I print out is below…these cars are very picky when it comes to battery voltage…you may have just enough to start it but the various modules and sensors need good voltage to operate correctly !!…if you have a tender I’d get the battery up to 12.6 (12.66 fully charged) and see what the voltage drops down to over a day or two !!

 

I'll see if I can get that done today at autozone or O' Reilly. Is there any battery that has proved to be better than another in these things? It's got an Optima Red Top in it now which the PO said is about a year old.

 

I’ve used the AC Delco Professional battery exclusively…an RC of 110 or 120 minutes is something you should consider…mine is 110.

 

I took the battery in to O' Reilly today, they tested it and said it's fine other than being a little low on charge. I put it on the charger for about half the day, got it up to 12.77 volts, started the car up and it started and idled just fine. I can turn the HVAC on and it doesn't drop the idle down to 300 like it was, it stays running and the a/c is cold. When I shift out of park into drive or reverse the RPM's kick up to about 1,100 for a second and then drop down to normal. I haven't driven the car yet to see if the hesitation is gone or not also.

 

It is also a good idea to perform a voltage drop check on the positive and negative side of the charging circuit…to check run the engine at idle with as much load you can put on it..to check positive side of charging by selecting a low voltage scale like 1 or 2 volts if your DVOM has that and connect red lead to alternator B+ stud and black lead to battery POSITIVE…to check ground side connect red lead to battery negative and red lead to a clean spot on the alternator housing…numbers should be .2 to .3 volts !!..I have .18 on positive and .10 on ground side !!…I’d also see how much your battery voltage drops overnight…write down the voltage before and then in the morning…hope you don’t have a parasitic drain !!…your battery was sitting at 12.0 volts you had said.