Traction system c1278

[Adam Calley]

I washed my car and now i can't even drive it or hardley start it. When i turn the key on i get the reduced engine power and service traction system messages on the display screen. Im getting the code c1278 which is a traction system code. When i clear it it comes right back. Im thinking a wheel speed sensor got water in it. Has anyone had this problem or know what i should check out. It will not even let me turn the traction control off either. Its a 1998 corvette. with the 99 and newer pcm with a custom os.

[joecar]

C1278 = TCS Temporarily Inhibited By PCM [set by the EBCM/ABS controller]

Sounds like you got water somewhere, maybe but not necessarily wheel sensors...

The GM Service Manual is very non-commital for this DTC...

1997 Chevrole Corvette DTC C1278 TCS Temporarily Inhibited By PCM




Circuit Description

The PCM monitors various parameters and will not allow Traction Control operation if any parameter falls beyond a predetermined value.
Conditions for Setting the DTC

A malfunction has been detected by the PCM. The PCM then causes TCS shutdown until the malfunction has been corrected.
Action Taken When the DTC Sets

This is a temporary operational malfunction. A malfunction DTC is stored, TCS is disabled and the Traction Control indicator is turned ON. ABS remains functional. If TCS is no longer inhibited the indicator will be turned OFF but the DTC will still be stored.
Conditions for Clearing the DTC

• Condition for DTC is no longer present and scan tool clear DTC function is used.
• Fifty ignition cycles have passed with no DTC(s) detected.

Diagnostic Aids

• This code is for information only. It indicates there are no problems in the ABS/TCS system, is used as an aid to the technician.

DTC C1278 TCS Temporarily Inhibited by PCM

Step
Action
Value(s)
Yes
No

1
Was the Diagnostic System Check performed?
--
Go to Step 2
Go to Diagnostic System Check

2

1. Turn the ignition switch to the ON position, engine OFF.
2. Using a scan tool, read ABS/TCS DTC(s).

Are any other DTC(s) set?
--
Go to that DTC table
Go to Step 3

3
Is DTC C1278 set as a current code?
--
Go to Step 5
Go to Step 4

4

1. Start engine and carefully test drive vehicle, achieving at least 16 Km/h (10 mph) while monitoring the scan tool for ABS/TCS DTC(s).
2. Repeat above drive cycle sequence two more times.

Did DTC C1278 set in the last three drive cycles
--
Go to Step 5
Go to Diagnostic System Check

5
Perform a Powertrain OBD System Check. Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls.
Did vehicle pass the OBD System Check?
--
Refer to Diagnostic Aids
Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls

1997 Chevrolet Corvette

[joecar]

1997 Chevrolet Corvette Powertrain On Board Diagnostic (OBD) System Check




Description

The Powertrain OBD System Check is an organized approach to identifying a problem created by an electronic engine control system malfunction. The Powertrain OBD System Check is the starting point for any driveability complaint diagnosis. The Powertrain OBD System Check directs the service technician to the next logical step in diagnosing a complaint. DO NOT PERFORM THIS CHECK IF NO DRIVEABILITY COMPLAINT EXISTS. Understanding and using the table correctly will reduce the diagnostic time and prevent the replacement of good parts.

Diagnostic Aids

This vehicle has a column lock system. This system is necessary because of the location of the ignition lock cylinder. The BCM controls a motor mounted on the steering column. The purpose of the motor is to unlock the steering wheel. The PCM will disable the fuel if the BCM is unable to determine if either the column is unlocked or vehicle speed is present. Refer to Body and Accessories for more information on the column lock system.
Important

If an intermittent condition exists, inspect the PCM wiring harnesses for improper installation of electrical components. Inspect for aftermarket theft deterrent devices, lights, and cellular phones. Ensure that no aftermarket equipment is connected to the Class 2 circuit. A cellular phone signal communication may cause an intermittent condition.

If multiple DTCs are set, inspect the IGN mini relay for proper operation. This relay protects the battery from a parasitic draw. The following components are powered by the IGN mini relay:

• Injectors/Ignition coils
• A/C system
• Transmission
• EVAP solenoid
• MAF sensor
• AIR pump and AIR solenoid relays
• TCC/Cruise and Extended Travel brake switches.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. Use a properly functioning scan tool with the diagnostic tables in this section. DO NOT use the Clear Info function unless instructed by a diagnostic procedure.
2. This check will determine if any other modules on the Class 2 circuit can communicate. If no communication occurs with any other module, the class 2 circuit is shorted to ground, is open, is shorted to a voltage, or one of the modules is causing no communications. Further diagnosis is required. Refer to Body and Accessories.
3. This step checks for DTCs associated with the Vehicle Theft Deterrent system which will prevent the engine from starting.
4. This condition may indicate a problem with the Column Lock system.
5. If multiple DTCs are stored, diagnose in the following order of priority:
   
   1. PCM/TAC failure DTCs (P0601, P0602, P0606, P1517, P1518, P1624)
   2. System Voltage DTCs
   3. Component level DTCs (Sensors, Solenoids, Relays etc.). Multiple DTCs within this category should be diagnosed in numerical order starting with the lowest numbered DTC.
   4. System level DTCs (Misfire, Fuel Trim, etc.)
   
   

For Automatic Transmission DTCs, Refer to Transmission/Transaxle/Automatic Transmission.
It is beneficial to review the Freeze Frame Data and/or Fail Records. Use the odometer information and the fail counter in order to determine how frequently and how recently the DTC set. This information and the other operating conditions when the DTC set may help diagnose an intermittent problem. Capturing the stored info preserves data that the PCM will lose when instructed to Clear Info at the end of a diagnostic table, or if you disconnect the PCM or replace the PCM during a diagnostic procedure. The scan tool stores the data in the scan tool's memory. Review the captured info at the end of the diagnostic procedure in order to catch the next DTC in the event there are multiple DTCs stored. Follow the order of priority as listed above.

1. Compare actual control system data with the values in the Engine Scan Tool Data List to determine if any parameter is not within limits. Keep in mind that a base engine problem (i.e. advanced cam timing) may substantially alter sensor values. If the actual data does not correspond with the values in the Engine Scan Tool Data List, refer to the appropriate system/component diagnostic aids or test descriptions.

Step
Action
Value(s)
Yes
No

1
Important

Check for applicable service bulletins before proceeding with diagnosis.

Important

Do not turn the ignition OFF when performing this Diagnostic table.

1. Connect a scan tool to the Data Link Connector (DLC).
2. Turn ON the ignition leaving the engine OFF.

Does the scan tool power-up?
--
Go to Step 2
Go to No Scan Tool Data

2
Does the scan tool display PCM data?
--
Go to Step 4
Go to Step 3

3
Use a scan tool in order to select the Diagnostic Circuit Check and the Class 2 Message Monitor.
Does the scan tool display any other Modules as Active?
--
Go to No Scan Tool Data
Go to Body and Accessories

4
Does the engine start and continue to run?
--
Go to Step 6
Go to Step 5

5
Is DTC P1626 or DTC P1631 stored?
--
Go to applicable DTC
Engine Cranks but Does Not Run

6
Does the engine continue to run after the vehicle has exceeded the specified speed?
3.2 km/h (2 mph)
Go to Step 7
Go to Body and Accessories for further diagnosis.

7
Observe the DTC information using a scan tool. Save the DTC Freeze Frame and/or Failure Records information (this option will display only if there is no previously captured data) or Refresh Info (in order to overwrite the older data with the current info) if DTC Status, last Test Failed, Test failed This Ignition, MIL Request, or History DTCs are set.
Are any DTCs displayed?
--
Go to the applicable DTC table
Go to Step 7

8
Compare the scan tool data with the values shown in the Engine Scan Tool Data List .
Are the values normal or within typical ranges?
--
Go to Symptoms
Go to Diagnostic Aids and Test Descriptions

1997 Chevrolet Corvette

[Adam Calley]

I am now getting the c1255 code, whicn i believe is a internal error in the ebtcm, do you think i would have to replace the whole unit?

[joecar]

I would try a few things first...

See if the EBCM module connector is loose or appears to have gotten wet...
disconnect/clean/reconnect it (use MAF clean to spray the pins, let air dry)...

Also check each wheel sensor in the same manner...

How "aggressively" did you apply water when washing the car...
water may have gotten into a connector at the wheel sensors or at the EBCM.

Also inspect the wiring from the EBCM to each of the wheel sensors,
see that nothing is cutting into any wire or conduit, and that no wire has been snagged out of the conduit.

You want to make sure the wiring, sensors, connectors are good/clean before sinking money into an EBCM.

Hmmm... I see that your EBCM is located behind IRS axle.

[joecar]

Look at this diagram... you may have gotten water in there.


1998 Chevrolet Corvette DTC C1255 EBTCM Internal Malfunction




Circuit Description

This DTC identifies a malfunction within the EBTCM.
Conditions for Setting the DTC

DTC C1255xx is set when an internal EBTCM malfunction exists.
Action Taken When the DTC Sets

ABS/TCS/Active Handling (if equipped with RPO JL4) are disabled.

• Indicators that turn on:
  
  • ABS indicator
  • Car Icon (TCS indicator)
  
  
• Messages displayed on the DIC:
  
  • Service ABS
  • Service Traction System
  • Service Active HNDLG (if equipped with Active Handling RPO JL4)
  
  

Conditions for Clearing the DTC

• Condition for DTC is no longer present and scan tool clear DTC function is used.
• Fifty ignition cycles have passed with no DTCs detected.

Diagnostic Aids

• When DTC C1255xx is displayed on the Scan Tool, it will be followed by two more numbers which should be noted along with any other DTCs that may be displayed. The additional two numbers displayed with DTC C1255xx are for aiding engineering to determine the cause of the internal malfunction.
• Make sure the integrity of the connection between the EBTCM and the BPMV is secure, tight, and free from corrosion.

DTC C1255xx EBTCM Internal Malfunction (ABS/TCS Disabled)

Step
Action
Value(s)
Yes
No

1
Was the Diagnostic System Check performed?
--
Go to Step 2
Go to Diagnostic System Check

2
Are any other DTC(s) present besides C1255xx?
--
Go to Applicable DTC Table. Refer to Diagnostic Trouble Code (DTC) List
Go to Step 3

3

1. Turn the ignition switch to the OFF position.
2. Disconnect the EBTCM.
3. Check for damaged, pushed out, or miswired terminals.

Was any damage found?
--
Go to Step 4
Go to Step 5

4
Repair as necessary.
Is the repair complete?
--
Go to Diagnostic System Check
--

5
Replace the EBTCM. Refer to Electronic Brake Control Module (EBCM) Replacement .
Is the replacement complete?
--
Go to Diagnostic System Check
--

1998 Chevrolet Corvette

[Adam Calley]

I sprayed pretty hard on it with a pressure washer, but not any harder than i usually do. I did pull the connector for the ebcm and didn't see any water though, the pins look pretty clean and no corrosion. I pulled the wheel sensor plugs also and didn't see any water. I will look over the wiring some more. I did pull the ebcm out and it looks fine and dry on the inside. Also i have had some loss of class communications codes every time I scan it, but those have been coming up for 2 years but never seemed to cause a problem. Also i have noticed a problem when i could drive it with the tcs system, sometimes while driving it all the sudden will quit pulling and have no power and it will say traction active, and i can turn off the tcs and then it will be fine and i didn't spin the tires at all, that has been happening for at least 2 years also but ive just been driving it with the tcs turned off. Do you think that would have any relation to whats going on now? Thanks for all your help.

[joecar]

Hmmm... sounds like it might be coincidental, TCS/EBCM may have been on it's way out already.

[Adam Calley]

Well I figured it out, it was the adapter plug going into the Ls2 90mm TB. It has a 5 or 6 pin connector that has some empty holes and the water got into the holes and don't ask me how that threw a tcs c1278 code. I blew it out and now it works fine. But i am getting maf codes and i need to get this thing inspected cause i our state requires it. I am using efi live custom os 02020003. I am getting the circuit high and low codes. For this os its supposed to be unplugged if im doing everything right i think and with the maf umplugged i get PO102 and P0103. When i plug it in i just get P0103. Do i need a new MAF sensor and if so what kind would you recommend I get. When i select them to not reported it won't hardley run at all and it won't take throttle. Also almost everytime i stop at a stop light it want to shut off. It also want to shut off alot when i put it in gear. Any suggestions for this Problem. Ive tried increasing my desired idle speeds and predicted idle air flow tables. and it doesn't seem to help.

[joecar]

Interesting... hmmm... ETC is part of the TCS, I suppose......good find... it pays to know your car...

If your tune is MAF-less (SD) then the PCM requires one of the MAF codes to be present (this is how the PCM knows to use the VE table).

Post your tune file.