: 99 sts won't start please help a newbie



99cadillacrick
01-30-10, 04:28 PM
Ok. So here we go. Was driving my 99 sts down the road and it just died out of no where. Would not start back up. Tested for spark and there was none. Tested for a injector pulse and nuthing also. Then tried to plug in the scanner to the computer port and it is telling me can not communicate with computer so went and pulled up the codes thru pushing the fan and info buttons on the dash and every code you could think of came up. Changed out the computer for a known good one and still in the same boat. Please help

Submariner409
01-30-10, 04:58 PM
You need to go back to the car's built-in code system, write down all the codes, whether they are Current or History, and use the "How to pull codes" sticky at the top of the main Northstar performance thread list to decipher what each means - open the URL in the sticky which has "obd2" in the address and use the lines in the Master Index to find the definitions of the P,B,C, and U codes.

99cadillacrick
01-30-10, 05:27 PM
Ok. I will do that first thing monday morning. The car is sitting inside my buddys shop. I need to wait for them to open monday and then I will go write them all down and see where it takes me. Thank you

Submariner409
01-30-10, 05:37 PM
FWIW the original PCM ("computer") is programmed with your particular car's VIN (Vehicle Identification Number), so it's entirely possible that you will now find some theft codes stored also, which will also disable the engine controls systems...............spark and injectors.

99cadillacrick
01-30-10, 07:02 PM
Yea I was guessing it might do that so did keep the old computer also. I tried to change just the prom also and still had no such luck.

Ranger
01-30-10, 09:41 PM
How old is the battery and what is the voltage? These cars will not run without a battery or with one that has low voltage an low voltage will set all sorts or false codes.

99cadillacrick
01-31-10, 06:37 PM
Hi. The battery is brand new after it died I thought it might be the battery but now it has a brand new battery in it. You can not scan the car with any kind of scanner. It says can not communicate with computer so the only way for me to check the codes is using the controls on the dash.

Ranger
01-31-10, 09:19 PM
Maybe the alternator died and is no longer charging it?

99cadillacrick
02-01-10, 01:10 PM
Just replaced the alternator when I did the battery so it is new also.

99cadillacrick
02-01-10, 01:23 PM
Ok. Just got all the codes. Have no idea where to start. There is a bunch of them. C1276 u1255 u1016 b1983 u1065 u1160 u1064 u1129 b1760 b1652 b1983 b1850 b1875 b2365 u1000 b2335 c1783 c1736

99cadillacrick
02-01-10, 03:32 PM
I have had 2 other shops say put 2 new crank sensors in it and it will start. Think that will make it run?

Submariner409
02-01-10, 03:56 PM
Use the sticky thread at the top of the page - "How to pull codes", go to the URL with "obd2" in the address, open the link, and use the lines in the Master Index to decipher your P,B,C, and U codes.

You do not show either P0335/6 or P0385/6 codes, so the CKP's aren't the first thing to suspect.........not that they aren't something to check, but without codes, you may be throwing money away. That's (CKPs) a $250+ shop job.

97EldoCoupe
02-01-10, 05:17 PM
1. Fuses
2. Grounds
3. Full scan with a Tech 2

There are 3 grounds that you need to check first. One large ground strap goes from the body to the alternator, one is a ground terminal off the rear of the RH cylinder head with about 8 wires running into it, and one is a ground strap from the RH cylinder head to the coil pack.

Does it crank over fast? Or slow like the battery's low/dead, even though it's fully charged....

In the fuse/relay center across from the power steering pump on the RH fender well, there will be all kinds of relays and fuses related to ignition and engine power feeds. Check fuses, swap relays, and see what you can come up with. Let us know and we'll help you as best as we can.

97EldoCoupe
02-01-10, 05:22 PM
And PCMs are VIN coded as Sub said- swapping the PCM in a Caddy won't help zilch unless you have a Tech2 and access to the binary files to upload.

Swapping PCMs will work in many other GMs- done it a time or two in Oldsmobile Auroras without a glitch but it's not going to happen in a Cadillac.

Mark C
02-01-10, 05:55 PM
If these are current, its one or more of these codes:

DTC U1000 Class 2 Communication Malfunction
DTC U1016 Loss of Communications with PCM
DTC U1065 Loss of Communications with IPM
DTC U1129 Loss of Communications with AMP
DTC U1160 Loss of Communications with DDM
DTC U1255 Class 2 Communication Malfunction
DTC U1255 Serial Data Line Malfunction

It would appear that your class 2 comm line is open circuited somewhere, maybe a loose connector.

Almost all of your B codes have to do with switches and sensors on the drivers side seat,


DTC B1760 Driver Seat Asm Rearward Switch CKT Malf
DTC B1850 Driver Lumbar Horiz Sensor CKT Malf
DTC B1875 Driver Belt Tower Down Sw CKT Malf
DTC B2355 Driver Front Vertical Sensor Malf (couldn't find 2335)
DTC B2365 Driver Rear Vertical Sensor Malf

except for;

DTC B1652 Loss of Keep Alive Memory (KAM)
DTC B1983 Device Power Circuit Low

Both of these are caused by a low or disconnected battery.


Two out of three of the C codes have to do with your air ride compressor and one of the communication lines to the ABS controller.

C1276 - Delivered Torque Signal Circuit Malfunction
C1736 - Compressor Relay Short to GND/Open Circuit
C1783 - ICCS2 DL Left Output Short Circuit to GND

Notice there isnt a single P code. I've seen a similar group of codes on my 97 when I had a a bad connection on the connector that is under the under hood fuse panel (on the drivers side shock tower). This connector has the the ICCS2 comm connections in it to the ABS controller, as well as a bunch of other stuff relating to the PCM power and some IPC comm lines. I know they moved the fure block to the other side of the car in 98 but I'd start looking at any underhood connectros that may be loose, or wet.

Of course all of these could be caused by that low voltage one B1983.

99cadillacrick
02-02-10, 12:14 AM
It turns over slow as if the battery is dead.

97EldoCoupe
02-02-10, 03:32 PM
I would assume if the battery shows 12.7 volts (fully charged) without the car running that you have a bad ground somewhere or the starter is drawing all the power away from the coils/injectors. Either way you need to get your starter speed up to par before going any further with the diagnosis.

99cadillacrick
02-02-10, 08:38 PM
Ok update for everyone. I went with my gut instinct and changed the crank sensors and what would you know it starts and runs like brand new. Have not tried to scan the car yet

97EldoCoupe
02-03-10, 12:51 AM
Glad it's working again. That's actually a learning experience for the rest of us - the CKPs can fail without throwing codes.... we owe you a thanks now, I'll remember this in case I run across the same thing someday.

Submariner409
02-03-10, 12:24 PM
:thumbsup: ..............highly unusual, though.