DTC Information

Sometimes in the Gretio app you will receive a error message when clearing DTCs

The error is one of:

“Conditions not Correct to clear DTCs. Try again later.”

“Sub function not supported.”

“Service not supported by this module.”

The App is working as intended. The vehicle is responding with these errors. General Motors restricts clearing DTCs under most circumstances.

You may find another scan tool device ‘clears’ the DTCs. However this is usually not the case. Most other scan tools do not check for the errors.  You may also receive these errors when following the GM Service Manual. The service manual contains many outdated procedures which still call for clearing DTCs. GM is aware of this issue.

Generally speaking, the vehicle DTCs can clear on their own after fixing the issue. No further action is needed. Historical PIDs may be ignored if the underlying issue has been resolved (they will clear after several drive cycles).

If a DTC clear is 100% required follow these steps:

  1. Turn off vehicle by pressing Push to start button or removing key.
  2. Disconnect any bluetooth, CarPlay, or Android Auto devices.
  3. Open and Close Driver Door. This will cause RAP power to turn off.
  4. Wait 30 seconds. If Gretio is connected, it may auto disconnect.
  5. [Key] Set ignition to Acc position
    [Push] Hold Push to Start Button without pressing brake until vehicle enters service mode. Do not start engine.
  6. Reconnect Gretio if Needed.
  7. Attempt DTC clear.

For DPF or SCR related DTCs you should follow the diagnostic guide . The diagnostic guide will have you perform a Def Quality Test or Service Bay Test depending on the error. These tests will give the vehicle the correct conditions to allow a DTC to clear.

Force Clear DTCs (Gretio 1.06.01 or newer)

Force clear DTCs will attempt to reset the module prior to clearing DTCs. This can help mimic a power cycle. It also retries numerous times.

Force clear DTCs will interrupt any active controls and PID scans.


Current DTCs are DTCs with an active (or very recent) fault. DTC will manage its Current flag based on its DTC Type.

Historical DTCs are DTCs which have been stored in long term memory. The DTC will mange its Historical flag based on its DTC Type.

Testing DTCs are like Pending DTCs. These are DTCs whose tests have not finished since either
1. This Drive Cycle
2. Since DTC cleared or DTC Failed

On all GM vehicles the DTC test functions control SCR and other errors. The DTCs must PASS for a SCR warning to disappear, or for a DEF Quality Test or Service Bay Test to complete. The group of DTCs which must PASS is documented in the service manual. A DTC will PASS when the conditions for running the DTC are present, and it does not lead to a Fault. When this happens the DTC will disappear from the Testing DTCs list.

EPA Readiness Monitors will only show ‘Ready’ after their corresponding DTCs PASS. Unfortunately, Gretio cannot see which DTCs are used for a given readiness monitor. This information is only found in the service information.

Important Takeaway: DTCs may lose both ‘Active’ and ‘Historical’ flags but not ‘PASS’.  SCR Warnings and Readiness Monitors are based on DTCs PASSing during the DTC Logic. Different DTCs perform their logic under different conditions which is usually documented in service information.

As such, an active SCR Warning may be present even if there is no active or historical DTC. The same situation occurs for readiness monitors.