Can anyone provide a definition of error codes P12FF and P26C8 as they pertain to a 2014 C7 or point me to a source for the info?

 

From the shop manual. Hope it helps.

2014 Chevrolet Corvette | Corvette VIN Y Service Manual 5533811 | Document ID: 3460638

DTC P12E3-P12E9, P12EA-P12EF, P12F0-P12F9, or P12FA-P12FF
Diagnostic Instructions
•Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
•Review Strategy Based Diagnosis for an overview of the diagnostic approach.
•Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptors
Note: Bank 1 refers to a valve on the left side of the vehicle. Bank 2 refers to a valve on the right side of the vehicle.

DTC P12E3
Cylinder Deactivation Exhaust Flow Valve Control Circuit Open

DTC P12E7
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit Low Duty Cycle (Bank 1)

DTC P12E8
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit High Duty Cycle (Bank 1)

DTC P12E9
Cylinder Deactivation Exhaust Flow Valve Open Position (Bank 1)

DTC P12EA
Cylinder Deactivation Exhaust Flow Valve Closed Position (Bank 1)

DTC P12EB
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit Low Frequency (Bank 1)

DTC P12EC
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit High Frequency (Bank 1)

DTC P12ED
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit Incorrect Frequency (Bank 1)

DTC P12EF
Cylinder Deactivation Exhaust Flow Valve Stuck Closed (Bank 1)

DTC P12F0
Cylinder Deactivation Exhaust Flow Valve Stuck Open (Bank 1)

DTC P12F1
Cylinder Deactivation Exhaust Flow Valve Position Not Learned (Bank 1)

DTC P12F2
Cylinder Deactivation Exhaust Flow Valve Actuator Performance (Bank 1)

DTC P12F4
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit Low Duty Cycle (Bank 2)

DTC P12F5
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit High Duty Cycle (Bank 2)

DTC P12F6
Cylinder Deactivation Exhaust Flow Valve Open Position (Bank 2)

DTC P12F7
Cylinder Deactivation Exhaust Flow Valve Closed Position (Bank 2)

DTC P12F8
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit Low Frequency (Bank 2)

DTC P12F9
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit High Frequency (Bank 2)

DTC P12FA
Cylinder Deactivation Exhaust Flow Valve Feedback Circuit Incorrect Frequency (Bank 2)

DTC P12FC
Cylinder Deactivation Exhaust Flow Valve Stuck Closed (Bank 2)

DTC P12FD
Cylinder Deactivation Exhaust Flow Valve Stuck Open (Bank 2)

DTC P12FE
Cylinder Deactivation Exhaust Flow Valve Position Not Learned (Bank 2)

DTC P12FF
Cylinder Deactivation Exhaust Flow Valve Actuator Performance (Bank 2)

Diagnostic Fault Information
Circuit
Short to Ground
Open/High Resistance
Short to Voltage
Signal Performance

Run/Crank Ignition 1 Voltage
—
P12E3, P12E7, P12EB, P12F4, P12F8
—
—

Exhaust Flapper Valve Feedback Signal
P12E7, P12E8, P12EB, P12EC, P12ED, P12F4, P12F5, P12F8, P12F9, P12FA
P12E7, P12E8, P12EB, P12EC, P12ED, P12F4, P12F5, P12F8, P12F9, P12FA
P12E7, P12E8, P12EB, P12EC, P12ED, P12F4, P12F5, P12F8, P12F9, P12FA
P12F2, P12FF

Exhaust Flapper Valve Control
P12E3
P12E3
P12E3
—

Ground
—
—
—
—


Circuit/System Description
The cylinder deactivation exhaust flow control system consists of valves installed at the inlet of the muffler. The exhaust flow control system is used to tune the exhaust note.

Conditions for Running the DTC
•Battery voltage must be between 9-16 V.
•The engine must be running.
Conditions for Setting the DTC
The chassis control module detects an open, short to ground or short to B+ on the cylinder deactivation exhaust flow control valve control circuit.

Actions Taken When the DTC Sets
•The cylinder deactivation exhaust flow control valves are disabled for the remainder of the ignition cycle.
•DTCs P12E3, P12E7, P12E8, P12E9, P12EA, P12EB, P12EC, P12ED, P12EF, P12F0, P12F1, P12F2, P12F4, P12F5, P12F6, P12F7, P12F8, P12F9, P12FA, P12FC, P12FD, P12FE and P12FF are all type B DTCs.
Conditions for Clearing the DTC
•The condition responsible for setting the DTC no longer exists.
•A history DTC will clear once 40 consecutive malfunction-free ignition cycles have occurred.
•DTCs P12E3, P12E7, P12E8, P12E9, P12EA, P12EB, P12EC, P12ED, P12EF, P12F0, P12F1, P12F2, P12F4, P12F5, P12F6, P12F7, P12F8, P12F9, P12FA, P12FC, P12FD, P12FE and P12FF are all type B DTCs.
Reference Information
Schematic Reference
Exhaust System Schematics

Connector End View Reference
Component Connector End Views

Description and Operation
Exhaust Tail Pipe Flow Control System Description and Operation

Electrical Information Reference
•Circuit Testing
•Connector Repairs
•Testing for Intermittent Conditions and Poor Connections
•Wiring Repairs
Scan Tool Reference
Control Module References for scan tool information

Circuit/System Verification
 1. Ignition ON.
 2. Verify DTCs U0109, P2534 or P2535 are not set.
⇒ If any of these DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

⇓ If none of these DTCs are set
 3. Verify that the cylinder deactivation exhaust flow control valve position not learned DTCs P12F1 or P12FE are not set.
⇒ If DTC P12F1 or P12FE are set
Perform the Exhaust Flow Control Valve Learn.

⇓ If DTC P12F1 or P12FE are not set
 4. Verify that nothing is preventing the cylinder deactivation exhaust flow control valves from moving freely. Such as debris, binding shafts or any type of damage.
⇒ If the cylinder deactivation exhaust flow control valves do not move freely
Repair the condition that is preventing the valves from moving freely.

⇓ If the cylinder deactivation exhaust flow control valves move freely
 5. Verify the cylinder deactivation exhaust flow control valves open and close when commanding the Cylinder Deactivation Exhaust Flow Valve On and Off with a scan tool. Command the valves open and closed through two key cycles and verify the DTC resets. The valves will make an audible noise when moving.
⇒ If the cylinder deactivation exhaust flow control valves do not open and close and DTC resets
Refer to Circuit/System Testing

⇓ If the cylinder deactivation exhaust flow control valves open and close and DTC does not reset
 6. All OK.
Cylinder Deactivation Exhaust Flow Control Valve Feedback Circuit

Valve 1 or Valve 2 Scan Tool Position Parameter Conversion Table

Out of Range
Valve Open
In Transition
Valve Closed
Out of Range

0–3
4–27
28–63
64–92
93–100


Circuit/System Testing
Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

Note: Do not replace the chassis control module based on a DTC stored in history. The DTC may be stored but that does not indicate a failure of the chassis control module. Refer to Strategy Based Diagnosis for further history DTC diagnostics.

 1. Ignition OFF and all vehicle systems OFF, disconnect the harness connectors at the Q15A Exhaust Flow Control Valve – Cylinder Deactivation Left and the Q15B Exhaust Flow Control Valve – Cylinder Deactivation Right. It may take up to 2 min for all vehicle systems to power down.
 2. Test for less than 5 Ω between the Q15A Exhaust Flow Control Valve – Cylinder Deactivation Left terminal 1 and ground.
⇒ If 5 Ω or greater
2.1. Ignition OFF.
2.2. Test for less than 2 Ω in the ground circuit end to end.
⇒ If 2 Ω or greater, repair the open/high resistance in the circuit.
⇒ If less than 2 Ω, repair the open/high resistance in the ground connection.
⇓ If less than 5 Ω
 3. Test for less than 5 Ω between the Q15B Exhaust Flow Control Valve – Cylinder Deactivation Right terminal 1 and ground.
⇒ If 5 Ω or greater
3.1. Ignition OFF.
3.2. Test for less than 2 Ω in the ground circuit end to end.
⇒ If 2 Ω or greater, repair the open/high resistance in the circuit.
⇒ If less than 2 Ω, repair the open/high resistance in the ground connection.
⇓ If less than 5 Ω
 4. Verify a test lamp illuminates between the Q15A Exhaust Flow Control Valve – Cylinder Deactivation Left Ignition circuit terminal 4 and ground.
⇒ If the test lamp does not illuminate and the circuit fuse is good
4.1. Ignition OFF, remove the test lamp.
4.2. Test for less than 2 Ω in the ignition circuit end to end.
⇒ If 2 Ω or greater, repair the open/high resistance in the circuit.
⇒ If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
⇒ If the test lamp does not illuminate and the circuit fuse is open
4.1. Ignition OFF, remove the test lamp.
4.2. Test for infinite resistance between the ignition circuit and ground.
⇒ If less than infinite resistance, repair the short to ground on the circuit.
⇒ If infinite resistance, replace the Q15A Exhaust Flow Control Valve – Cylinder Deactivation Left.
⇓ If the test lamp illuminates
 5. Verify a test lamp illuminates between the Q15B Exhaust Flow Control Valve – Cylinder Deactivation Right Ignition circuit terminal 4 and ground.
⇒ If the test lamp does not illuminate and the circuit fuse is good
5.1. Ignition OFF, remove the test lamp.
5.2. Test for less than 2 Ω in the ignition circuit end to end.
⇒ If 2 Ω or greater, repair the open/high resistance in the circuit.
⇒ If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
⇒ If the test lamp does not illuminate and the circuit fuse is open
5.1. Ignition OFF, remove the test lamp.
5.2. Test for infinite resistance between the ignition circuit and ground.
⇒ If less than infinite resistance, repair the short to ground on the circuit.
⇒ If infinite resistance, replace the Q15B Exhaust Flow Control Valve – Cylinder Deactivation Left.
⇓ If the test lamp illuminates
 6. Connect a test lamp between the Q15A Exhaust Flow Control Valve – Cylinder Deactivation Left control circuit terminal 2 and B+, ignition ON.
 7. Verify the test lamp transitions between dimly illuminated and brightly illuminated when commanding the Cylinder Deactivation Exhaust Flow Control Valves Open and Closed with a scan tool.
⇒ If the test lamp is always OFF
7.1. Ignition OFF, disconnect the harness connector at the K38 Chassis Control Module.
7.2. Test for less than 1 V between the control circuit and ground.
⇒ If 1 V or greater, repair the short to voltage on the circuit.
⇒ If less than 1 V, replace the K38 Chassis Control Module.
7.3. Test for less than 2 Ω in the control circuit end to end.
⇒ If 2 Ω or greater, repair the open/high resistance in the circuit.
⇒ If less than 2 Ω, replace the K38 Chassis Control Module.
⇒ If the test lamp is always ON
 8. Connect a test lamp between the Q15B Exhaust Flow Control Valve – Cylinder Deactivation Right control circuit terminal 2 and B+, ignition ON.
 9. Verify the test lamp transitions between dimly illuminated and brightly illuminated when commanding the Cylinder Deactivation Exhaust Flow Control Valves Open and Closed with a scan tool.
⇒ If the test lamp is always OFF
9.1. Ignition OFF, disconnect the harness connector at the K38 Chassis Control Module, Ignition ON.
9.2. Test for less than 1 V between the control circuit and ground.
⇒ If 1 V or greater, repair the short to voltage on the circuit.
⇒ If less than 1 V, replace the K38 Chassis Control Module.
9.3. Test for less than 2 Ω in the control circuit end to end.
⇒ If 2 Ω or greater, repair the open/high resistance in the circuit.
⇒ If less than 2 Ω, replace the K38 Chassis Control Module.
⇒ If the test lamp is always ON
9.1. Ignition OFF, disconnect the harness connector at the K38 Chassis Control Module.
9.2. Test for infinite resistance between the control circuit and ground.
⇒ If less than infinite resistance, repair the short to ground on the circuit.
⇒ If infinite resistance, replace the K38 Chassis Control Module.
⇓ If the test lamp transitions between dimly illuminated and brightly illuminated
10. Ignition OFF and all vehicle systems OFF, disconnect the harness connectors at the left and right Q15 Exhaust Flow Control Valve-Cylinder Deactivation and the K38 Chassis Control Module, ignition ON.
11. Test for less than 1 V between the exhaust flow control valve-cylinder deactivation feedback circuit terminals listed below and ground:
◦K38 Chassis Control Module connector X1 terminal 10
◦K38 Chassis Control Module connector X1 terminal 7
⇒ If 1 V or greater
Repair the short to voltage on the circuit.

⇓ If less than 1 V
12. Ignition OFF.
13. Test for infinite resistance between the exhaust flow control valve-cylinder deactivation feedback circuit terminals listed below and ground:
◦K38 Chassis Control Module connector X1 terminal 10
◦K38 Chassis Control Module connector X1 terminal 7
⇒ If less than infinite resistance
Repair the short to ground on the circuit.

⇓ If infinite resistance
14. Test for less than 2 Ω between the exhaust flow control valve-cylinder deactivation feedback circuit terminals listed below:
◦K38 Chassis Control Module connector X1 terminal 10 and Q15A Exhaust Flow Control Valve-Cylinder Deactivation Left terminal 3
◦K38 Chassis Control Module connector X1 terminal 7 and Q15B Exhaust Flow Control Valve-Cylinder Deactivation Right terminal 3
⇒ If 2 Ω or greater
Repair the open/high resistance in the circuit.

⇓ If less than 2 Ω
15. Replace the appropriate exhaust flow control valve-cylinder deactivation actuator left or right (Bank 1 or Bank 2) as referred to by the DTC that is set.
16. Verify the DTC does not set while operating the vehicle within the Conditions for Running the DTC.
⇒ If the DTC sets
Replace the K38 Chassis Control Module.

⇓ If the DTC does not set
17. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.

•Exhaust Control Valve Actuator Replacement
•Exhaust Flow Control Valve Learn
•Control Module References for chassis control module replacement, programming, and setup.

----------------------------------------------------------------------------

DTC P26C8
Diagnostic Instructions
•Perform the Diagnostic System Check - Vehicle Prior to using this diagnostic procedure.
•Review Strategy Based Diagnosis for an overview of the diagnostic approach.
•Diagnostic Procedure Instructions provides an overview of each diagnostic category.
DTC Descriptor
DTC P26C8
Chassis Control Module Requested MIL Illumination

Circuit/System Description
The chassis control module constantly monitors the chassis control system for any condition which may adversely affect vehicle emissions. If a condition is detected, the chassis control module sets a DTC and sends a serial data message to the engine control module (ECM). The ECM sets DTC P26C8 to inform the technician that the chassis control module has set the emission related DTC. The serial data message sent by the chassis control module also contains a request for the ECM to illuminate the malfunction indicator lamp (MIL).

The technician can observe the DTC that was set by the chassis control module by reviewing the ECM Freeze Frame records on the scan tool. The ECM Freeze Frame records also contain the engine operating conditions present when the chassis control module DTC set.

Conditions for Running the DTC
The ignition is ON, or the engine is running for greater than 3 s.

Conditions for Setting the DTC
The ECM receives a serial data message from the chassis control module indicating that an emission related DTC has set in the chassis control module.

Action Taken When the DTC Sets
•DTC P26C8 is a Type A DTC.
•DTC P26C8 will continue to be current or active as long as the chassis control module is requesting MIL illumination.
Conditions for Clearing the DTC
DTC P26C8 is a Type A DTC.

Diagnostic Aids
Communication codes, U-codes, as well as powertrain codes, P-codes, set in the chassis control module will cause the chassis control module to request DTC P26C8 to be set in the ECM.

Reference Information
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference
Control Module References for scan tool information

Circuit/System Verification
Note:

◦Do not replace the engine control module for this DTC. DTC P26C8 is an informational DTC.
◦Correct any engine control and communication DTCs before diagnosing chassis control module DTCs.
 1. Verify there are no engine control or communication DTCs set.
⇒ If a DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

⇓ If a DTC is not set
 2. Verify there are no chassis control module DTCs set.
⇒ If a DTC is set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

⇓ If a DTC is not set
 3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
 4. Verify the DTC does not set.
⇒ If the DTC sets
Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

⇓ If the DTC does not set
 5. All OK.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.

 

Thank you 3X2! That is what I needed to know.