P1645 – OBD-II DTC

OBD-II DTC P1645 – Powertrain DTCs Available in Another Module

DTC P1645 meaning

DTC P1645 indicates that there are powertrain diagnostic trouble codes (DTCs) available in another module. This code is often set when the Engine Control Module (ECM) detects that another module, such as the Transmission Control Module (TCM) or Body Control Module (BCM), has stored DTCs that have not been addressed. The presence of this code suggests a communication issue or a fault in the related modules.

DTC P1645 symptoms

Common symptoms associated with DTC P1645 may include:

• Check Engine Light (CEL) illuminated
• Reduced engine performance
• Transmission shifting issues
• Inconsistent vehicle behavior
• Other DTCs present in related modules

DTC P1645 causes

The causes of DTC P1645 can vary, but typical reasons include:

• Faulty communication between modules
• Corrupted or damaged wiring and connectors
• Faulty ECM or other control modules
• Software issues or outdated firmware
• Electrical interference or shorts

DTC P1645 seriousness

DTC P1645 can be considered serious as it indicates that there are unresolved issues in other modules that could affect vehicle performance and safety. Ignoring this code may lead to further complications, including potential damage to the engine or transmission, and could result in a failure to pass emissions tests.

How to diagnose DTC P1645

To diagnose DTC P1645, follow these steps:

1. Use an OBD-II scanner to retrieve the DTCs from all modules.
2. Check for any additional DTCs that may provide more context.
3. Inspect wiring and connectors for damage or corrosion.
4. Verify communication between the ECM and other modules.
5. Check for software updates or reprogramming needs.
6. Perform a visual inspection of the vehicle’s electrical system.

How to fix DTC P1645 step-by-step instructions

To fix DTC P1645, follow these steps:

1. Clear the DTCs using an OBD-II scanner.
2. Address any other DTCs found in related modules.
3. Repair or replace damaged wiring and connectors.
4. Reprogram or update the ECM and other modules if necessary.
5. Test drive the vehicle to ensure the issue is resolved.
6. Recheck for any new or recurring DTCs.

How to erase DTC P1645

To erase DTC P1645, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn the ignition key to the “On” position without starting the engine.
3. Access the DTC menu on the scanner.
4. Select the option to clear or erase DTCs.
5. Confirm the action and wait for the scanner to complete the process.
6. Disconnect the scanner and start the vehicle to verify that the code does not return.

Recommended tools for OBD-II diagnostics

Explore our expert picks: The Best OBD2 Scanners for 2025

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.