The code P0785: Shift/Timing Solenoid “A” Malfunction points to a malfunction in the shift/timing solenoid “A” of the transmission system. This issue could stem from various causes, such as electrical problems, mechanical failures within the transmission, or issues with the Transmission Control Module (TCM).
P0785 quick overview
| Meaning | P0785: Shift/Timing Solenoid “A” Malfunction |
| Is it serious? | Yes, this code indicates a malfunction in the transmission’s shift solenoid, which can affect the vehicle’s shifting behavior and overall performance. |
| Possible causes | – Faulty or damaged shift solenoid – Wiring or connector issues in the transmission system – Malfunctioning Transmission Control Module (TCM) – Low or dirty transmission fluid – Internal transmission mechanical problems |
| How to diagnose? | Check Transmission Fluid: Verify fluid level and condition. Inspect Wiring and Connectors: Look for damage or corrosion in transmission wiring. Test Shift Solenoid: Use diagnostic tools to evaluate solenoid function. Scan for Additional Codes: Check for other transmission-related diagnostic trouble codes. Evaluate TCM: Assess the Transmission Control Module for issues or the need for reprogramming. Examine Valve Body: Inspect the transmission’s valve body for signs of wear or damage. |
P0785 Meaning
The P0785 code means there’s a problem with one of the solenoids that control when and how your car shifts gears. It’s like having a tiny traffic cop inside your car’s transmission that’s not doing its job right, which can make your car shift gears poorly or even cause damage if not fixed. It’s important to get this checked out to keep your car running smoothly.
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How to fix P0785 – learn from mechanics
I looked into P0785 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.
Case #1: Chevrolet
Vehicle Information
- 1997 Chevrolet C1500, 4.3L
Issue + Repair History
- Issue: PO785 code sets 15 seconds after start-up
- Repair History: Replaced 3-2 Solenoid, but no change
Other OBD2 Codes + Test Results
- Code PO785
Suggestions from Community
- Check if there’s an early and late solenoid with different resistance
- Possible issues with the ignition switch
- Monitor voltage at pin 13 during startup for any flickering, indicating a PCM issue
- Suggested to try a known good PCM
Final Fix
- Replaced PCM, resolved the issue. Vehicle was sent to the dealer for PCM programming and repair was done under the 8/80 emissions warranty.
Case #2: Saab
Vehicle Information
- 2003 Saab 9-3 Linear, 2.0L
Issue + Repair History
- Issue: Transmission in limp mode, code P0785 (shift circuit SLS, battery plus)
- Repair History: Rebuilt transmission, replaced SLS solenoid
Other OBD2 Codes + Test Results
- Code P0785 – Transmission in limp mode
Suggestions from Community
- Recommended using a Tech 2 for diagnosis
Final Fix
- Replaced Transmission Control Module (TCM), resolved the issue after reprogramming at the dealer
Case #3: GMC
Vehicle Information
- 1997 GMC Jimmy SL, 4.3L
Issue + Repair History
- Issue: Service Engine light intermittent, stored code P0785, 3rd gear starts usually after cold start and short trips
- Repair History: Checked connections, replaced 3-2 shift solenoid, serviced transmission, amp flow tested solenoid
Other OBD2 Codes + Test Results
- Code P0785
Suggestions from Community
- Check for ignition switch issues, possible ground problems inside PCM, alternator and battery health, and inspect wiring and PCM connections
Final Fix
- Replaced Vehicle Control Module (VCM), reprogrammed by dealer, resolved the issue
Case #4: Volkswagen
Vehicle Information
- 2003 Volkswagen EuroVan GLS, 2.8L
Issue + Repair History
- Issue: Towed in due to crank/no start situation
- No previous history known
Other OBD2 Codes + Test Results
- P0010 – Camshaft Actuator Circuit Bank 1 Position A
- P0753 – Solenoid A
- P0758 – Solenoid B
- P0763 – Solenoid C
- P0768 – Solenoid D
- P0773 – Solenoid E
- P0785 – Shift/Timing Solenoid
- No spark detected
Suggestions from Community
- Check if under factory warranty
- Verify signal from crankshaft sensor
- Investigate potential speed sensor issues
- Consider using Vag-Com from Ross Tech for transmission module interrogation
- Test G38 and G68 sensors as per Alldata procedures
Final Fix
- Vehicle was sent to the dealer for further diagnostics and repair; awaiting update from customer on the specific problem and solution.
Case #5: Volvo
Vehicle Information
- 2001 Volvo V70 X/C, 2.4L
Issue + Repair History
- Initially, engine running rough with a long start time
- Replaced battery, spark plugs, and cam sensor
- After replacing cam sensor, engine did not start
Other OBD2 Codes + Test Results
- P0237 – Turbocharger Boost Sensor A Circuit Low
- P0303 – Cylinder #3 Misfire Detected
- P0340 – Camshaft Position Sensor A Circuit
- P0343 – Camshaft Position Sensor A Circuit High Input B1
- P1618 – Manufacturer Controlled Computer Output Circuit
- P0785 – Shift/Timing Solenoid Malfunction
- P0335B – Crankshaft Position Sensor A Circuit Malfunction
Suggestions from Community
- Revisit cam sensor installation
- Consider the possibility of a bad new cam sensor
- Check the crank sensor located on top of the bellhousing
- Examine the VVT solenoid wires under the spark plug cover
- Consider issues with the engine’s wiring harness
- Inspect for VVT problems or incorrect cam timing
- Confirm cam and crank sensors are in sync
Final Fix
- Realized that the crank sensor connector was disconnected while replacing the cam sensor
- Reconnected the crank sensor, and the engine started immediately
- Replaced the turbo boost sensor (MAP sensor) after which the engine ran much better
How to diagnose P0785
I made you an overview of solving this DTC, based on all the advice that was suggested by certified mechanics to address this issue in previously mentioned service cases.
| Advice | Diagnostic Step Description for P0785 Code |
|---|---|
| Inspect Transmission Wiring and Connectors | Check all transmission-related wiring and connectors for damage or corrosion. |
| Verify Shift Solenoid Operation | Test the shift solenoids to ensure they are functioning correctly. |
| Check Power Supply to Solenoids | Ensure the solenoids are receiving the correct power supply. |
| Scan for Additional Codes | Use a scan tool to check for other related codes that might indicate a broader issue. |
| Test Transmission Control Module (TCM) | Evaluate the TCM for faults or programming issues. |
| Examine Valve Body and Internal Components | Inspect the transmission’s valve body and internal components for any signs of wear or failure. |
| Consider Fluid Condition and Level | Check the transmission fluid for quality and level, as it can impact solenoid operation. |
Car Diagnostics Training
- Car Electrical basics
- OBD-II scanner basics
- How to use an OBD reader
- Introduction to a Bi-directional Scan tool
- OBD scanner buyer’s guide + discounts
I test OBD-II scanners and make DIY Engine diagnostics guides to help you solve your car problems without having to depend on the mechanic. A lot of them will try to scam you or are just no help at all. About Juraj Lukacko