What Does P1783 Mean?
The TCM has detected an electrical malfunction in the transmission reverse input circuit. This is similar to P1778 and indicates problems with the circuit that signals when reverse gear is selected or engaged.
Common Causes
36%
Faulty reverse input switch or sensor
30%
Damaged wiring harness or poor connections in reverse circuit
20%
Faulty transmission range sensor
9%
Internal transmission harness damage or fluid intrusion
5%
TCM internal circuit failure
Diagnostic Steps
1
Step 1: Verify reverse gear engages properly and reverse lights function
2
Step 2: Test voltage and continuity at reverse input circuit with gear in reverse and other positions
3
Step 3: Inspect transmission range sensor connector for corrosion or damaged pins
4
Step 4: Check internal transmission connector for fluid contamination
5
Step 5: Compare reverse input signal values to manufacturer specifications using scan tool
Estimated Repair Cost
$200 - $850
Parts + labor, varies by vehicle and location
The TCM has detected an electrical malfunction in the transmission reverse input circuit. This is similar to P1778 and indicates problems with the circuit that signals when reverse gear is selected or engaged.
The most common cause of P1783 (Transmission Reverse I/P Circuit Malfunction) is: Faulty reverse input switch or sensor
Typical repair costs for P1783 range from $200 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May prevent reverse gear engagement or cause unintended reverse operation. Use extreme caution when parking on inclines.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1783 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System
Difficulty
Type
Manufacturer
Recommended Tools
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