P1736 Transmission 1-2 Shift Fault
The P1736 code indicates that the Transmission Control Module (TCM) or Powertrain Control Module (PCM) has detected a failure during the 1-2 upshift in an automatic transmission. The control module continuously monitors engine RPM, transmission input and output speeds, and hydraulic actuator response to verify that the expected gear ratio is achieved within programmed time and tolerance. If the 1-2 shift is not completed correctly due to a hydraulic, electrical, or mechanical anomaly, this manufacturer-specific code is stored, typically triggering transmission protection protocols.
01. Most Common Causes
- Faulty, stuck, or obstructed shift solenoid or control valve
- Low, degraded, or contaminated automatic transmission fluid (ATF)
- Insufficient hydraulic pressure in the clutch or band circuit for the 1-2 shift
- Internal wear or damage to friction discs, bands, or planetary components
- Short circuit, open circuit, or corroded connectors in wiring between PCM/TCM and transmission solenoids
- Erratic input or output speed sensor readings interfering with shift timing
02. Symptoms You Will Notice
- Harsh or delayed 1-2 upshift
- Transmission slipping or flaring during gear change
- Check Engine Light or Transmission Warning Light illuminated
- Transmission stuck in limp mode or failsafe gear
- Poor acceleration or reduced fuel economy
03. Step-by-Step Diagnosis
Scan for codes and record freeze frame data
Check transmission fluid level, condition, and color
Inspect wiring and connectors to solenoids and speed sensors for damage or corrosion
Test shift solenoid resistance and operation with a multimeter or scan tool
Perform hydraulic pressure test to verify clutch/band circuit pressure
If necessary, remove transmission pan to inspect for debris and mechanical wear
1. Frequently Asked Questions
Is it safe to drive?▼
Driving with P1736 is not recommended. The transmission may shift harshly, slip, or enter limp mode, which can cause further internal damage and create a safety hazard.
How much does it cost to fix?▼
Repair costs vary widely: simple solenoid replacement or fluid change can be $150-$400, while internal transmission rebuild or replacement may range from $1,500 to $4,000 or more.