BYD Song Plus Transmission Slipping? Here's What to Check First

Understanding the Problem

If your BYD Song Plus automatic transmission is slipping between gears with a delayed, jerky engagement, it's usually a sign of low or degraded transmission fluid, a failing valve body, or a sensor issue. The good news is that not all causes require a full rebuild—often it's a matter of checking fluid first.

Likely Causes

• Low or dirty transmission fluid — The most common and easiest fix. Check the dipstick (if equipped) or have a shop inspect fluid level and condition.
• Faulty transmission speed sensors — These sensors (input/output shaft speed sensors) send data to the TCM. When they fail, the transmission may shift erratically or slip.
• Worn valve body or solenoids — The valve body controls hydraulic pressure for gear changes. Sticking solenoids or a worn valve body can cause hesitation and harsh shifts.
• Throttle position sensor (TPS) issues — If the TCM doesn’t get accurate throttle input, it may delay or mismanage shift points.

Which Sensors and Parts to Check First

• Transmission fluid level and condition — Warm up the car, park on level ground, and check fluid on the dipstick. It should be bright red/pink and not smell burnt.
• Diagnostic trouble codes (DTCs) — Use an OBD-II scanner to pull codes related to transmission sensors (e.g., P0715, P0720, P0740).
• Input/output speed sensors — Located on the transmission housing. Clean or replace if they show erratic resistance readings.
• Valve body solenoids — A transmission shop can test solenoid resistance and flow; in some cases a solenoid pack replacement is needed.

Is It Safe to Keep Driving?

In short—no. Driving with slipping gears and jerky engagement can quickly worsen internal damage (clutch packs, bands, torque converter). If the transmission is low on fluid, you may lose hydraulic pressure entirely. Have the car towed to a shop for a fluid check and diagnostic scan. Continuing to drive risks a complete transmission failure that would be far more expensive to repair.

This material is AI-generated and for informational purposes only — it does not replace an in-person diagnosis by a qualified mechanic.