Diagnostic procedure

WARNING: This page is about a different car, the 2005 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

DTC U2021 DIAGNOSTIC PROCEDURE

STEP	INSPECTION		ACTION
1	CHECK WHETHER ENGINE HAS WARMED UP Has engine warmed up?	Yes	Go to the next step.
1	CHECK WHETHER ENGINE HAS WARMED UP Has engine warmed up?	No	Warm up the engine. If TCS OFF light goes out, system is normal.
2	VERIFY THAT MALFUNCTION SYMPTOM OCCURS AFTER ENGINE IS WARMED UP Warm up the engine. Is TCS indicator light also illuminated and DTC C1119 obtained?	Yes	Go to DTC C1119 chart.
2		No	If TCS OFF light goes out, system is normal. If TCS OFF light does not goes out, go to the next step.
3	VERIFY TROUBLESHOOTING COMPLETED Clear the DTC from the memory. (See CLEARING DTCS PROCEDURES ) Is same DTC present?	Yes	Replace ABS/TCS HU/CM, then go to the next step.
3		No	Go to the next step.
4	VERIFY AFTER REPAIR PROCEDURE Is there any other DTC present?	Yes	Go to the applicable DTC inspection.
4		No	Troubleshooting completed.