P1790 GMC Code - Transmission Control Module Checksum
Quick Answer
P1790 GMC indicates Transmission Control Module Checksum. Common causes include Faulty Transmission Control Module, Transmission Control Module harness is open or shorted, Transmission Control Module circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P1790 GMC indicates Transmission Control Module Checksum.
- Common causes
- Common causes include Faulty Transmission Control Module, Transmission Control Module harness is open or shorted, Transmission Control Module circuit poor electrical connection.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P1790 GMC Description
What are the Possible Causes of the DTC P1790 GMC?
- Faulty Transmission Control Module
- Transmission Control Module harness is open or shorted
- Transmission Control Module circuit poor electrical connection
How to Fix the DTC P1790 GMC?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P1790 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Frequently Asked Questions about P1790 GMC Code
1. What does the OBDII code P1790 mean on a GMC vehicle?
P1790 indicates a Transmission Control Module (TCM) checksum error, meaning the TCM has detected inconsistencies or corruption in its data or programming.
2. What are the common symptoms of a P1790 code in a GMC?
Symptoms may include erratic shifting, transmission slipping, poor acceleration, the vehicle stuck in limp mode, or the check engine light turning on.
3. What causes the P1790 code to appear?
The code can be triggered by corrupted TCM software, a failed TCM, faulty wiring or connectors, or power supply issues affecting the TCM.
4. Can I drive my GMC with a P1790 code?
Driving with a P1790 code is not recommended, as it may lead to further transmission issues or leave the vehicle in limp mode, limiting performance.
5. How do you diagnose a P1790 code on a GMC?
Diagnosis typically involves scanning for additional codes, inspecting TCM-related wiring and connectors, testing the TCM's power and ground circuits, and checking for software updates.
6. Can a P1790 code be fixed by resetting the TCM?
In some cases, resetting or reprogramming the TCM may clear the code, but the underlying issue must be addressed to prevent recurrence.
7. How much does it cost to fix a P1790 code on a GMC?
Repair costs can vary, ranging from $100 for simple wiring repairs to $1,500 or more for TCM replacement, depending on the vehicle and diagnosis.
8. Does a P1790 code always mean the TCM needs replacement?
No, the issue may be related to wiring, software, or power supply problems, so a thorough inspection is essential before replacing the TCM.
9. Can a P1790 code be caused by a weak battery on a GMC?
Yes, a weak or failing battery can cause voltage drops or interruptions, potentially triggering the P1790 code.
10. Do I need to update my TCM software to fix a P1790 code?
In some cases, updating the TCM software can resolve the code if the issue is related to software corruption or outdated programming.
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