diff --git a/firmware/controllers/algo/obd_error_codes.h b/firmware/controllers/algo/obd_error_codes.h
index 70517a2e42..b773118f13 100644
--- a/firmware/controllers/algo/obd_error_codes.h
+++ b/firmware/controllers/algo/obd_error_codes.h
@@ -2082,7 +2082,7 @@ typedef enum {
 	CUSTOM_ERR_TASK_TIMER_OVERFLOW = 6722,
 	CUSTOM_NO_ETB_FOR_IDLE = 6723,
 	CUSTOM_ERR_6724 = 6724,
-	CUSTOM_ERR_6725 = 6725,
+	CUSTOM_ERR_CJ125_DIAG = 6725,
 	CUSTOM_ERR_VVT_OUT_OF_RANGE = 6726,
 	CUSTOM_ERR_6727 = 6727,
 	CUSTOM_ERR_6728 = 6728,
diff --git a/firmware/hw_layer/sensors/cj125_logic.cpp b/firmware/hw_layer/sensors/cj125_logic.cpp
index 85543f59cc..d188354080 100644
--- a/firmware/hw_layer/sensors/cj125_logic.cpp
+++ b/firmware/hw_layer/sensors/cj125_logic.cpp
@@ -76,6 +76,9 @@ void CJ125::printDiag() {
 		printDiagCode(logger, "UN", diag >> 2, LOW_VOLTAGE);
 		printDiagCode(logger, "IA", diag >> 4, LOW_VOLTAGE);
 		printDiagCode(logger, "HR", diag >> 6, "open load");
+/* todo: do we want to throw CRITICAL on diag start-up error? probably not?
+		firmwareError(CUSTOM_ERR_CJ125_DIAG, "CJ125 is not well");
+*/
 	}
 }
 
diff --git a/hardware/CJ125_board/readme.md b/hardware/CJ125_board/readme.md
index b84a48d254..88f7752b59 100644
--- a/hardware/CJ125_board/readme.md
+++ b/hardware/CJ125_board/readme.md
@@ -2,4 +2,8 @@
 
 [iBom](https://rusefi.com/docs/ibom/O2_input_CJ125_latest.html)
 
-2019 status: known to work, but documentation is very limited :(
\ No newline at end of file
+2019 status: known to work, but documentation is very limited :(
+
+On this board UR and UA do NOT have build-in resistor dividers.
+
+There is an opinion that for open air UA divider is required.
\ No newline at end of file