a week ago shift linkage bushing broke. i fixed it and drove car 2 days. was coming home from work in torential downpour with no problems. the next day got in to go to work and car would turn over but not start. codes are: pcm- no comm, tcs c1241hc,1276hc,1255hc-bcm u1255hc-bo-rfa u1016hc. most of the codes would clear but the no comm on pcm. am getting loss of power,low fuel,service abs,etc on display. do you think the pcm got water logged during storm? am at wits end .any help is appriciated. 98 c5 with duel ram air intake and no eng mods. thx for any help

 

Does the engine hit at all?

I had a problem like this when i put an ls6 into my 97. The pcm was not communicating with the bcm. I had to do a 30 min. procedure to connect the different computers. I will repost with the learn procedure once i get home. For now pull up a diagram of all the ground points and check/clean them. With all those codes for the tcs and pcm, you may have a ground begin to oxidize with all the water. Also pull the access panel under the passenger side fender/behind the front tire and check out the pcm. look for any obvious water staining/ damage. check out the panel/cover to see if it was broken or not sealing properly. Good luck, keep us posted.

 

if the pcm did get wet it won't crank and given the symptoms you described it seems like it. Mine got wet twice before I found a large hole in the inner fender well.

 

Check your grounds. There is a major one on each side of the car. From the sounds of what you described having just worked on the steering check the drivers side where the ground strap attaches to the block. If that has come loose, your injectors won't fire so the car will turn over but won't run.

 

well the hot texas sun dried out my pcm. all codes but magna stear are gone and car has had that since i bought it. now i need to find out how it got wet. carpet in passenger side bone dry. small amount of water from ac is seen. guess i will pull battery and milk the udder(sounds strange!)and pull tire and remove panel and see what i can see. my thanks to all who responded!

 

never got to check for water at pcm. floor is dry, some water is draining from ac. today i was sitting in pking lot eating lunch when everything went dead, tryed to start and nothing. cked codes and most from before were there. tried to crank again and cranked right up. cleared all codes as before. would lack of wet floor make to more of a ground problem or could something else be going on, again thanks for any help and yes i know i should have cked pcm and under battery but sort of put it off since it was running again!

 

I would start with checking and cleaning the grounds. I'd also check the battery. Current fluctuations can give these cars fits. Start there and if that's not it we will rack our brains some more.

 

how old is the battery?

 

not sure how old battery is. it went dead when shift linkage broke. trany was in reverse and backup lights stayed on. put it on charger and havent had any problems that i know of. if no date on batt will a load test show anything?

 

Yeah it'll show if the battery is good or not, like proletariat designs pointed out start with the simple stuff like battery and cleaning the grounds.

 

also when car went dead in pking lot i mean dead with no radio,no lights on dash or anything. cycled switch several times and then cranked with codes which then cleared when i reset them. will see if battery has a date. thx

 

DEAD (to me) means NOTHING at all electrical is functioning. You need to be careful when you say DEAD.

An easy and simple electrical system test is to test the horn, pull the HIGH BEAM stalk back etc.... and see if the headlights flash. Those things are connected more or less directly to the battery. If those work, then the electrical system is not totally dead. If they don't, here are some starting points on problem resolution:

1. Disconnect the battery terminals. Measure the battery directly at the battery terminals with a DC Volt meter.

2. Clean the battery terminals with a small Stainless Steel wire brush.

3. Examine the battery terminals and the CRIMP CONNECTOR under the black and red plastic cover. Look for corrosion and or heat damage.

4. Reinstall the battery terminals. Positive terminal and then the Negative . To properly tighten the battery terminals they should be TORQUED to 11 ft/lbs. (as per the service manual) IF,,,,,,,,, you can move a battery cable (by hand) it is NOT correctly tightened and could be causing your issues.

once the battery is checked and the cables are properly tightened, read the DTCs using the DIC. "CLEAR ALL OF THEM"



Then see if the car will crank and start and run normally. If not, read and then post the DTCs that come back.

The PCM is in an area that is NOT water tight. It is exposed to moisture/water frequently. All of the connections are weather tight and the PCM case is sealed. SO,,,, unless something is really wrong with the PCM and the PCM connectors, a rain storm should NOT usually cause any issues.

The BCM is NOT water tight. It is in an area that SHOULD NOT be exposed to moisture...... HOWEVER,,,,,, If the HVAC air box drain gets clogged, or the windshield cowl drains UDDERS get clogged, the BCM can and will get wet. Usually you will feel a wet carpet but, sometimes the water does not wet the top of the carpet. Move the passengers seat fully forward and pull up the carpet on the back wall to expose the back of the floor carpet. Feel the carpet jute insulation under the carpet under the seat. If it is wet or damp, your BCM got wet.

If you can beep the horn and flash the lights but when you turn the key and the engine will not crank,,,, you have an issue in the STARTER/THEFT DETERRENT CRANK Circuit. Use the schematic below to see what might be causing the theft deterrent relay to not provide high current 12 VDC to the starter solenoid. Check all those fuses in this circuit!



Hope this helps.

Bill