What Does P1782 Mean?
The TCM is unable to communicate properly with the engine control module to request ignition timing retard during shifts. This coordination is necessary for smooth transmission operation and preventing engine flare during gear changes.
Common Causes
35%
Communication fault between TCM and ECM on data bus
25%
Failed TCM unable to send retard signal
20%
Failed ECM not responding to retard requests
15%
Damaged or corroded data bus wiring or connectors
5%
Software calibration issue requiring reprogramming
Diagnostic Steps
1
Step 1: Check for additional communication-related codes in both TCM and ECM
2
Step 2: Test CAN bus communication lines for proper voltage and resistance
3
Step 3: Inspect wiring and connectors between TCM and ECM for damage or corrosion
4
Step 4: Verify both modules have proper power and ground connections
5
Step 5: Check for available software updates or TSBs for both control modules
Estimated Repair Cost
$200 - $1,500
Parts + labor, varies by vehicle and location
The TCM is unable to communicate properly with the engine control module to request ignition timing retard during shifts. This coordination is necessary for smooth transmission operation and preventing engine flare during gear changes.
The most common cause of P1782 (Ignition Retard Request Circuit Fault) is: Communication fault between TCM and ECM on data bus
Typical repair costs for P1782 range from $200 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
May cause harsh or erratic shifts and potential engine flare during gear changes. Continued operation may damage transmission components.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1782 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System / Engine Management
Difficulty
Type
Manufacturer
Recommended Tools
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