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Hi guys,
I have a 2009 Convertible 6.2L. All of a sudden I got bunch of OBD error codes with Check Engine Engine Light.
Confirm main battery health before proceeding. A weak battery will take you on a wild goose chase after spurious DTCs. Load test if necessary. No-load voltage should be 12.5V-ish. Make sure the battery terminals are clean and tight. Make sure the starter connection is clean and tight. Replace the battery if it's old or was ever run dead.
After you've ruled all that out, work on the codes.
Confirm main battery health before proceeding. A weak battery will take you on a wild goose chase after spurious DTCs. Load test if necessary. No-load voltage should be 12.5V-ish. Make sure the battery terminals are clean and tight. Make sure the starter connection is clean and tight. Replace the battery if it's old or was ever run dead.
After you've ruled all that out, work on the codes.
Torquetube, thank you for your reply
The battery is fairly new.
I tested the voltage when the car was OFF, it was 12V +.
When the car was running , it is 14V.
ECU voltage was also 14.04 V
OBD voltage was 13.3V
I also removed the battery, cleaned the terminals.
I cleaned 2 grounds to the body as well under the battery, on the passenger side.
I checked the voltage with different ground points , and they were good.
I reinstalled the battery, and the connection is pretty tight.
I got the additional codes I mentioned above after I did all that.
I am also suspecting if this has anything to do with the random misfires P0300.
The car has random misfire issue on all cylinders when it's idle.
I am considering replacing ignition coils as well just in case.
The car has 150,000 miles.
Can H normally goes from 2.5 volts to 3.5 volts and CAN L from 2.5 down to 1.5 volts with engine running…you would normally see these voltages with a scope because these voltages are so fast and I measure them
in microseconds (millionth of a second)…with ignition on you would see 2.7 volts on CAN H and 2.3 volts on CAN L…if you’re seeing .88 volts sounds like the Bus is shorted to ground…as far as misfires the coil packs are pretty much bulletproof…take some time diagnosing and don’t fire the parts canon.
Thank you for your reply.
Your reply is very informative with pictures.
I like it very much.
Unfortunately, I don't have a scope but I am planning to get one.
I followed some instructions from youtube.
I didn't measure voltages for CAN H and CAN L when the car was running or when the ignition was ON.
I should do that.
While the ignition was OFF Voltage Reading ..
[[b]CAN high signal --> Body Ground] 0.88 to 1.2 Volt
[[b]CAN low signal --> Body Ground] 0.88 to 1.2 Volt
While the ignition was OFF Resistance Reading ..
[[b]CAN high signal --> Body Ground] No Value / Open Line
[[b]CAN low signal --> Body Ground] No Value / Open Line
The video said,
if there was a short to Battery, the voltage should be approximately same with Battery Voltage.
If there was a short to Ground , the resistance should NOT be open line.
My reading is very low voltage with open line .
OBD says BUS A. I don't know which circuit is BUS A.
U0073 [0xC073] Control module - data bus Off Control Module Communication
Bus A Off Short to Battery; Control Module Communication Bus A Off Short to Ground; Control Module Communication Bus A Off Open; ECU HS Bus Off; ECU LS Bus Off
My Radio is acting weird.
There might be a problem with Radio circuit.
i don't know. I have to check.
May be I should remove the fuse for the radio and check.
I am thinking , if the short to battery was because of a cable, then most likely I was going to get battery voltage.
If the short is coming from an electronic board with low voltage, that's why I might be getting low voltage reading.
TCM might be causing the issue too.
i don't know how to check that one.
I will try to remove the TCM fuse under the hood #1, and try it again.
P0700 [0x0700] Transmission control system, MIL request - circuit malfunction
I also have random misfires.
They could all be related.
Ignition OFF - CAN H Voltage Ignition OFF - CAN L Voltage Ignition OFF - CAN H OHM Open Line Ignition OFF - CAN L OHM Open Line Ignition ON - CAN H Voltage Ignition ON - CAN L Voltage Ignition Running - CAN H Voltage Ignition Running - CAN L Voltage Ignition ON - Not Running - DTC No U or C Codes (ABS/EBCM/ESC) Ignition Running - Additional Codes - Page 1 Ignition Running - Additional Codes - Page 2 Additional ABS/EBCM/ESC Codes C0450 C0561 U0073 U0100 U0101 U0140 Ignition Running - Additional Codes - Page 3
OBD Output when the Ignition is ON but NOT running.
Car Scanner ELM OBD2
Version: 1.104.0/1.104.0/iOS
DTC report
Connection profile: Chevrolet OBD-II / EOBD (2004 - n.d.) + CANDate: 3/13/2024 12:50:07 PM
============================ Engine control unit
DTCs: 2
---------------------------- P0300 [0x0300] Random/multiple cylinder(s) - misfire detected
General Electrical Failures [0x00]
Status:
DTC supported by calibration,
Current DTC,
Test failed since DTC cleared,
History DTC, Test not passed since current power up,
Warning Indicator Requested
---------------------------- P0856 [0x0856] Traction control input signal - malfunction
General Electrical Failures [0x00]
Status:
DTC supported by calibration,
Test failed since DTC cleared,
History DTC, Test not passed since current power up
============================
Transmission control unit #2
No DTC found.
============================
EHU (Entertainment Head Unit)
No DTC found.
Car Scanner ELM OBD2
Version: 1.104.0/1.104.0/iOS
DTC report
Connection profile: Chevrolet OBD-II / EOBD (2004 - n.d.) + CANDate: 3/13/2024 12:53:19 PM
============================
Engine control unit
DTCs: 2
---------------------------- P0300 [0x0300] Random/multiple cylinder(s) - misfire detected
General Electrical Failures [0x00]
Status: DTC supported by calibration, Current DTC, Test failed since DTC cleared, History DTC, Test not passed since current power up, Warning Indicator Requested ---------------------------- P0856 [0x0856] Traction control input signal - malfunction
General Electrical Failures [0x00]
Status: DTC supported by calibration, Test failed since DTC cleared, History DTC ============================
Transmission control unit #2
No DTC found.
============================ ABS/EBCM/ESC
DTCs: 6
---------------------------- C0450 [0x4450] Steering Assist Control Solenoid Valve Circuit Malfunction; Steering Assist Control Solenoid Valve Circuit Open; Steering Assist Control Solenoid Valve Circuit Performance - Signal Invalid; Steering Assist Control Solenoid Valve Circuit High Current
Algorithm Based Failures: plausibility failure [0x5A]
Status: DTC supported by calibration, Current DTC, History DTC, Current DTC since power up, Warning Indicator Requested ---------------------------- C0561 [0x4561] System Disabled Information Stored Engine Speed Out of Range; System Disabled Information Stored Acceleration Pedal Position Out of Range; System Disabled Information Stored Transmission Gear Invalid Data
Bus Signal/Message Failures: invalid serial data received [0x71]
Status: DTC supported by calibration, History DTC ---------------------------- U0073 [0xC073] Control module - data bus Off
Control Module Communication Bus A Off Short to Battery;
Control Module Communication Bus A Off Short to Ground;
Control Module Communication Bus A Off Open;
ECU HS Bus Off;
ECU LS Bus Off
General Electrical Failures [0x00]
Status: DTC supported by calibration, History DTC
---------------------------- U0140 [0xC140] Data bus, body control module (BCM) - no communication
Lost Communication With Body Control Module Performance - Signal Invalid;
Lost Communication With Body Control Module Invalid Data;
Lost Communication With Body Control Module Message Counter Incorrect;
Lost Communication With Body Control Module Bus Signal Checksum Error;
Data bus, body control module (BCM) - no communication;
General Electrical Failures [0x00]
Status: DTC supported by calibration, History DTC
---------------------------- U0101 [0xC101] Data bus, transmission control module (TCM) - no communication
Lost Communication With Transmission Control Module Invalid Data
General Electrical Failures [0x00]
Status: DTC supported by calibration, History DTC
---------------------------- U0100 [0xC100] Data bus, engine control module (ECM) A - no communication
Lost Communication With Engine Control Module Invalid Data;
Lost Communication With Engine Control Module Message Counter Incorrect;
Lost Communication With Engine Control Module Bus Signal Checksum Error
General Electrical Failures [0x00]
Status: DTC supported by calibration, History DTC
============================ EHU (Entertainment Head Unit)
No DTC found.
My Radio is acting weird.
There might be a problem with Radio circuit.
i don't know. I have to check.
May be I should remove the fuse for the radio and check.
There are two buses in a C6: the CAN bus (GMLAN), and the Class 2 bus. The radio is on the Class 2 bus, along with the instrument panel, door controls, the HVAC, the RCDLR, etc. The BCM has a Class 2 interface, too. It acts as the bridge between the two buses.
When the Class 2 bus gets stomped on, you usually get key fob problems because the RCDLR doesn't work.
It looks like your scan tool is able to communicate successfully with modules on the CAN bus. Some of the DTCs are comms errors, but some of them are sensor malfunctions. That looks a lot like a power or ground problem.
There are two buses in a C6: the CAN bus (GMLAN), and the Class 2 bus. The radio is on the Class 2 bus, along with the instrument panel, door controls, the HVAC, the RCDLR, etc. The BCM has a Class 2 interface, too. It acts as the bridge between the two buses.
When the Class 2 bus gets stomped on, you usually get key fob problems because the RCDLR doesn't work.
It looks like your scan tool is able to communicate successfully with modules on the CAN bus. Some of the DTCs are comms errors, but some of them are sensor malfunctions. That looks a lot like a power or ground problem.
TorqueTube,
Thank you for your reply and info.
I posted some videos related to Grounds and Traction Control Module.
I don't know where it is.
I think this whole thing is related to Traction Control Module including it's ground.
I will post again if I can find out more info.
Someone suggested the blue Left Connector under the Passenger Feet area is causing this problem because of loose connection.
I guess some passengers are putting pressure on the connector.
i will check that out.
Someone else suggested to clean the ground for Traction Control Module.
Thank you for your reply and info.
I posted some videos related to Grounds and Traction Control Module.
I don't know where it is.
I think this whole thing is related to Traction Control Module including it's ground.
I will post again if I can find out more info.
Someone suggested the blue Left Connector under the Passenger Feet area is causing this problem because of loose connection.
I guess some passengers are putting pressure on the connector.
i will check that out.
Someone else suggested to clean the ground for Traction Control Module.
Thanks again.
There is no separate traction control module. Traction control is managed by the EBCM (the ABS computer) with requests to the ECM (the engine computer).
The EBCM is integrated into the brake module at the left front of the engine bay. The ECM is behind the right front wheel well splash guard. The BCM is in the passenger footwell. The TCM (automatics only) is inside the gearbox.
There is no separate traction control module. Traction control is managed by the EBCM (the ABS computer) with requests to the ECM (the engine computer).
The EBCM is integrated into the brake module at the left front of the engine bay. The ECM is behind the right front wheel well splash guard. The BCM is in the passenger footwell. The TCM (automatics only) is inside the gearbox.
Thank you for that info. That helps a lot. Now it makes more sense.
I will check the and clean the Ground Connection for EBCM (ABS Computer) at the Left Front of the Engine Bay.
I will also check the connectors of BCM in the passenger footwell.
Someone under the comments of those videos said that after he added break fluid, his traction and service ride control messages went away.
I will check the break fluid as well.
I checked the Blue connectors at the BCM and they were tight.
I didn't unplug them. I didn't know how, and I didn't want to force them.
Traction Control Switch, at the center console, gets power from Interior Lights System (Gry/Wht) and Grounds (Blk) at Base of Right "A" Pillar
(Attached pdf Page 2 of 2 at the bottom right )
Traction Control Switch connects to (Brn/Wht)Body Control Module (BCM) (1571 / 68 ) mounted on Toe Board In Right Footwell.
(Attached pdf Page 2 of 2 at the center right )
I am not sure when it turns off the Traction Control, when it has power (closed circuit ) , or when it has no power ( open circuit ).
I am wondering if the ground is a common ground with the radio at base of right "A" pillar.
I will research that.
I checked the Blue connectors at the BCM and they were tight.
I didn't unplug them. I didn't know how, and I didn't want to force them.
They don't usually come loose, but the contacts get dirty. To unplug, squeeze the blue housing and swing the grey lever over. The connector will be ejected by cam action. No need to pull on it.
They don't usually come loose, but the contacts get dirty. To unplug, squeeze the blue housing and swing the grey lever over. The connector will be ejected by cam action. No need to pull on it.
Thanks TorqueTube. Like you said, the connection is pretty tight.
I found out some more info.
2009 EBCM is little different than the previous versions.
I took the attached photo.
I found some part numbers but I am not sure which one it is.
20777858 , 20777859 , 20777906 , 25780206
I also attached a technical bulletin from GM.
It may be a related issue.
2009 - 2011 Corvette: GM TechLink: Electronic Brake Control Module Communication
03-12-2024, 04:05 PM
2009 Conv 6.2L LS3 CAN Wiring Diagram Troubleshooting
