Where is the PCM grounded?

 

do u have the dtc code #s list the current ones,the ones that have the c by the#

 

yeah, they are listed earlier, basically: everything NO COMM

 

go back through all the areas you touched, check for a plug pin that may have backed out of the plug or a wire that may have got cut. a lot of problems are tied together with the computer system.
good luck
dennis

 

i know theres a ground behind the head if its loose u will have night mares with the car

 

Since you didn't have this problem until you disconnected your battery to do your stereo/deadening install I would retrace your steps and check every connector you pulled apart and every new connection you made to provide power to your stereo as well as all grounds. Any connection you had to loosen and then retighten should be checked as well. It sounds like something maybe drawing power that shouldn't be and causing the PCM to lose communication with the sensors it looks at when you start the car. These cars are very finicky electrically and installing a stereo system in them is not like it used to be in our old hot rods. Good luck and keep us up to date.

 

UPDATE:

took out the aftermarket head unit, and the car is FINE. So its a problem with my head unit, im not sure HOW it causes the problem, but its the case! Thanks for the help

Somehow, my after market head unit is FRIED though. <shrug>

 

 

PCM has grounds on the back of the drivers head. thew are in the wireing harness..

 

The head unit you put in the car was probably not compatible with the class 2 bus or there was a problem in the radio. When you get No Com that is an indication the Class 2 Bus is shorted to ground or a voltage and the modules cannot communicate. Here is the write up for the NO COM message (notice the referenced U codes cannot be read until the short is cleared):

Scan Tool Does Not Communicate with Class 2 Device
Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation when operating information and commands are exchanged among the modules. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes. Multiple diagnostic trouble codes (DTCs) may be set due to this malfunction and during this diagnostic procedure. Complete the diagnostic procedure in order to be sure all the DTCs are diagnosed and cleared from memory.

Diagnostic Aids
When the class 2 serial data circuit is shorted to ground, U1300 will be set. Refer to DTC U1300 .
When the class 2 serial data circuit is shorted to B+, U1301 will be set. Refer to DTC U1301 .
Disconnecting modules and turning the ignition switch to RUN may cause DTCs in the vehicle modules. Check for DTCs in each module upon completion of the required repair.

The following modules communicate on the class 2 serial data circuit:

Body Control Module (BCM)
Electronic Brake Control Module (EBCM)
Electronic Suspension Control (ESC)
HVAC (with CJ2)
Sensing and Diagnostic Module (SDM)
Instrument Panel Cluster (IPC)
Driver Door Module (DDM)
Passenger Door Module (PDM)
Seat Control Module (SCM) (with AAB)
Powertrain Control Module (PCM)
Radio
Remote Control Door Lock Receiver (RCDLR)


DTC U1300
Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation when operating information and commands are exchanged among the modules. In addition to this, Node Alive (State of Health) messages are transmitted by each module on the class 2 serial data circuit about once every two seconds. When the module detects no messages and a low voltage on the class 2 serial data circuit for approximately three seconds, U1300 is set and the setting of all other class 2 serial communication DTCs is inhibited.

Conditions for Running the DTC
Voltage supplied to the module is in the normal operating voltage range.
The module setting the DTC requires serial data communication to occur.
Conditions for Setting the DTC
No valid messages are detected on the class 2 serial data circuit.
The voltage level detected on the class 2 serial data circuit is low.
The above conditions are met for approximately three seconds.
Action Taken When the DTC Sets
The module inhibits the setting of all other class 2 DTCs.
The module uses default values for all parameters received on the class 2 serial data circuit.
Conditions for Clearing the DTC
A current U1300 will clear when a valid class 2 message is detected on the class 2 serial data circuit or at the end of the current ignition cycle.
A history U1300 will clear upon receipt of a scan tool Clear DTCs command or after 50 ignition switch cycles with no repeated failure.
Diagnostic Aids
This DTC cannot be retrieved with a current status. Diagnosis of a current U1300 is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to Scan Tool Does Not Communicate with Class 2 Device .
An intermittent condition is likely to be caused by a short to ground on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to Scan Tool Does Not Communicate with Class 2 Device .

DTC U1301
Circuit Description
Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation when operating information and commands are exchanged among the modules. In addition to this, Node Alive (State of Health) messages are transmitted by each module on the class 2 serial data circuit about once every two seconds. When the module detects no messages and a high voltage on the Class 2 serial data link for approximately three seconds, U1301 is set and the setting of all other class 2 serial communication DTCs is inhibited.

Conditions for Running the DTC
Voltage supplied to the module is in the normal operating voltage range.
The module setting this DTC requires serial data communication to occur.
Conditions for Setting the DTC
No valid class 2 messages are detected on the class 2 serial data circuit.
The voltage level detected on the class 2 serial data circuit is high.
The above conditions are met for approximately three seconds.
Action Taken When the DTC Sets
The module inhibits the setting of all other class 2 DTCs.
The module uses default values for all parameters received on the class 2 serial data circuit.
Conditions for Clearing the DTC
A current U1301 will clear when a valid class 2 message is detected on the class 2 serial data circuit or at the end of the current ignition cycle.
A history U1301 will clear upon receipt of a scan tool Clear DTCs command or after 50 ignition switch cycles with no repeated malfunction.
Diagnostic Aids
This DTC cannot be retrieved with a current status. Diagnosis of a current U1301 is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to Scan Tool Does Not Communicate with Class 2 Device .
An intermittent condition is likely to be caused by a short to voltage on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to Scan Tool Does Not Communicate with Class 2 Device.

Hope this helps you isolate the problem with the head unit.

Bill

 

Thanks a ton for the help!

I picked up a Pioneer unit (had Alpine) and plugged it in... Worked flawlessly. I think there's a short inside the alpine.

 

Dayum. I hope this was a cut and paste.

Charlie

 

HECK.... BILL just did that easy one from memory
he's the electrical guru

 

Glad to hear you found the problem.

 

Never mind...