diff --git a/firmware/controllers/algo/engine.cpp b/firmware/controllers/algo/engine.cpp
index 0f873c755e..1e55e60032 100644
--- a/firmware/controllers/algo/engine.cpp
+++ b/firmware/controllers/algo/engine.cpp
@@ -192,9 +192,9 @@ void Engine::updateTriggerWaveform() {
 }
 
 #if ANALOG_HW_CHECK_MODE
-static void assertCloseTo(const char * msg, float actual, float expected) {
-	if (actual < 0.75 * expected || actual > 1.25 * expected) {
-		firmwareError(OBD_PCM_Processor_Fault, "%s analog input validation failed %f vs %f", msg, actual, expected);
+static void assertCloseTo(const char * msg, float actual, float expected, float lowRatio, float highRatio) {
+	if (actual < lowRatio * expected || actual > highRatio * expected) {
+		firmwareError(OBD_PCM_Processor_Fault, "%s validation failed actual=%f vs expected=%f", msg, actual, expected);
 	}
 }
 #endif // ANALOG_HW_CHECK_MODE
@@ -249,8 +249,13 @@ void Engine::periodicSlowCallback() {
 #if ANALOG_HW_CHECK_MODE
 	efiAssertVoid(OBD_PCM_Processor_Fault, isAdcChannelValid(engineConfiguration->clt.adcChannel), "No CLT setting");
 	efitimesec_t secondsNow = getTimeNowSeconds();
+
+#if ! HW_CHECK_ALWAYS_STIMULATE
+	fail("HW_CHECK_ALWAYS_STIMULATE required to have self-stimulation")
+#endif
+
 	if (secondsNow > 2 && secondsNow < 180) {
-		assertCloseTo("RPM", Sensor::get(SensorType::Rpm).Value, HW_CHECK_RPM);
+		assertCloseTo("RPM", Sensor::get(SensorType::Rpm).Value, HW_CHECK_RPM, 0.9, 1.1);
 	} else if (!hasFirmwareError() && secondsNow > 180) {
 		static bool isHappyTest = false;
 		if (!isHappyTest) {
@@ -259,10 +264,11 @@ void Engine::periodicSlowCallback() {
 			isHappyTest = true;
 		}
 	}
-	assertCloseTo("clt", Sensor::get(SensorType::Clt).Value, 49.3);
-	assertCloseTo("iat", Sensor::get(SensorType::Iat).Value, 73.2);
-	assertCloseTo("aut1", Sensor::get(SensorType::AuxTemp1).Value, 13.8);
-	assertCloseTo("aut2", Sensor::get(SensorType::AuxTemp2).Value, 6.2);
+	assertCloseTo("clt", Sensor::get(SensorType::Clt).Value, 49.3, 0.75, 1.25);
+	assertCloseTo("iat", Sensor::get(SensorType::Iat).Value, 73.2, 0.75, 1.25);
+	assertCloseTo("aut1", Sensor::get(SensorType::AuxTemp1).Value, 13.8, 0.75, 1.25);
+	// huh? why such a wide gap? smaller resistor delta causes large temperature delta on the left side of the curve?
+	assertCloseTo("aut2", Sensor::get(SensorType::AuxTemp2).Value, 6.2, 0.75, 2);
 #endif // ANALOG_HW_CHECK_MODE
 }