4209A4
High4209A4 — Transmission Overheating: Reduced Power Limp Mode
Description
What the Code Means
4209A4 is a transmission control module (EGS) code that logs when ATF temperature exceeds the thermal protection threshold. In response, the TCM puts the transmission into Hot Mode 3 — a thermal limp state: engine torque is reduced and the torque converter may lock up to limit further heat buildup.
Common causes are low ATF level, degraded fluid past its service life, or excessive load on the transmission.
Symptoms
Symptoms
- transmission overheat warning;
- reduced power (torque limitation);
- torque converter lockup;
- harsh, rough shifts.
Causes and fixes
Diagnosis and Repair
- Check ATF level and condition. If the fluid shows signs of burning, replace it.
- Check the transmission cooler (heat exchanger) for blockages — reduced flow capacity leads to ATF overheating.
- Check the cooling system: radiator, fan.
- After fixing the cause, reset the EGS adaptations.
Possible secondary damage
Secondary Damage
- prolonged overheating damages the torque converter;
- clutch packs degrade;
- the valve body is damaged;
- the result is total transmission failure, so don't put off fixing the cause.