P0789 OBD-II Trouble Code: Shift/Timing Solenoid Intermittent

Our certified mechanics come to you · Get a fair and transparent estimate upfront

Red-stars EXCELLENT RATING ON

Cost of diagnosing the P0789 code

P0789 is a diagnostic trouble code (DTC) for "Shift/Timing Solenoid Intermittent". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate Credit towards follow-up repair Earliest Availability
Ford$20.00
Toyota$20.00
BMW$20.00
SCHEDULE P0789 DIAGNOSTIC Get a fair and transparent estimate upfront

P0789 code definition

When the Powertrain Control Module (PCM) detects a problem in the shift/timing solenoid, a P0789 trouble code is stored. Some codes that could accompany a P0789 trouble code include P0785, P0786, P0787, and P0788.

What the P0789 code means

Using calculations based on the position of the throttle, vehicle speed, engine speed, and engine load, the PCM determines the appropriate gear ratio. If the desired gear ratio does not correspond with the actual gear ratio, a P0789 trouble code is stored and a Check Engine Light illuminates. In some makes and models, a Check Engine Light is not automatically illuminated, requiring multiple failure first.

What causes the P0789 code?

The cause of a P0789 trouble code usually stems from a faulty shift solenoid, though other causes include blockage inside the transmission fluid passages or a mechanical failure of the transmission. Low fluid levels or dirty transmission fluid can also cause the storage of this code, in addition to a faulty PCM or Transmission Control Module (TCM).

What are the symptoms of the P0789 code?

The mechanic might find a variety of symptoms associated with this trouble code. These include no detectable symptoms, a failure of the transmission to shift into one or more gears, slippage of the transmission, and overheating of the transmission. Some final symptoms are a decrease in the vehicle's fuel efficiency and the TCM placing the transmission into Limp-in mode.

How does a mechanic diagnose the P0789 code?

To diagnose a P0789 trouble code, the mechanic needs an advanced scanner, digital volt/ohmmeter, manual pressure gauge, and a hydraulic pressure diagram for the vehicle. To diagnose the trouble code, the mechanic needs to perform the following:

  • Check all of the wiring, connectors, and components for damage. When replacing wiring, connectors, and components, the mechanic might need to replace the full internal transmission harness.

  • Pull the dipstick out and check the level and condition of the transmission fluid.

  • If the fluid looks abnormal or smells burnt, drop the transmission pan and look for evidence of debris. Debris can indicate a more far reaching problem with the transmission itself.

  • After making all of the necessary repairs to the internal transmission, the mechanic should fill the transmission with enough fluid to repair any leaks.

  • Once the leaks are repaired, the mechanic should fill the transmission fluid to a normal level, start the vehicle, and allow the engine to reach a normal operating temperature.

  • The mechanic should clear the code and take the vehicle for a test drive.

  • If the code returns, connect a manual pressure gauge to the transmission to check the hydraulic pressure pump. The mechanic should use a hydraulic pressure diagram when doing so.

  • The mechanic should then compare their findings with the manufacturer's specifications to find any discrepancies.

  • If the code persists, the mechanic can use the digital volt/ohmmeter to check the reference voltage and ground signal of the shift solenoid.

  • If the reference voltage or ground signal check out as open, the mechanic should then check for continuity and resistance in all of the related circuits. The mechanic should make sure to disconnect any control modules in the circuit to avoid damage.

  • If everything else checks out, inspect the PCM to see if it is at fault.

  • Finally, After making all of the necessary repairs, the mechanic should clear the code and retest the system to see if it returns.

Common mistakes when diagnosing the P0789 code

Mechanics commonly assume a faulty shift solenoid circuit is at the root of the problem. This leads to the replacement of one or more shift solenoids in error, and failure to ultimately clear the code.

How serious is the P0789 code?

A P0789 trouble code can be an indicator of more serious problems and if left undiagnosed and unfixed can ultimately lead to transmission failure. The mechanic needs to clear trouble codes in the order they were stored in order to successfully determine the cause of a P0789 trouble code.

What repairs can fix the P0789 code?

Repairing and clearing a P0789 trouble code requires a mechanic to perform the following steps:

  • Replace any defective or otherwise damaged wiring, connectors, or components. This usually requires the mechanic to replace the full internal transmission harness.

  • Rebuild the transmission if internal transmission damage is detected. The mechanic should also install a replacement torque converter when completing this repair.

  • Repair any leaks before filling the transmission fluid to an appropriate level to test drive the vehicle.

  • Replace the hydraulic pump if the pump pressure reads low. Mechanics should keep in mind that when replacing the hydraulic pump they need to remove the transmission and partially disassemble it.

  • Replace any shift solenoids, or solenoid packs that test as at fault during a diagnosis of the wiring connectors and other components. The mechanic should disconnect any related control modules before performing this repair to avoid damage and control module memory loss.

  • Replace the PCM if it is detected as faulty.

Need help with a P0789 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

P0789
trouble codes
Check Engine Light

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0789 code.

SCHEDULE P0789 DIAGNOSTIC
Get a $20 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating


YourMechanic Check Engine Light is on Inspection Service

Average Rating

4.8/5

Number of Reviews

5,606

Rating Summary
5,180
205
50
34
137
5,180
205
50
34
137

James

40 years of experience
34 reviews
James
40 years of experience
Ford F-150 - Check Engine Light is on - Chagrin Falls, Ohio
Jim was great! Arrived on time, quickly diagnosed the problem and recommended further work. Very helpful, I’ll use Jim again and recommend to family and friends.

Roberto

11 years of experience
137 reviews
Roberto
11 years of experience
Nissan Titan - Check Engine Light is on - Spring, Texas
Roberto was very thorough with his explanation of repairs needed. I will contact your mechanic for future repairs.

Matthew

32 years of experience
839 reviews
Matthew
32 years of experience
Kia Optima - Check Engine Light is on - Yorktown, Virginia
Matthew Lerman was God Sent, and thank God for Your Mechanic,, you have my Vote Looking , Looking forward for more Business. Very Honest Guy

Robert

20 years of experience
38 reviews
Robert
20 years of experience
Honda Accord - Check Engine Light is on - Brentwood, California
He came earlier than on time and got the job done faster than I seen anyone else have . Solid honest hard working dude.


More related articles

P2764 OBD-II Trouble Code: Torque Converter Clutch Pressure Control Solenoid Control Circuit Low
P2764 means the system is receiving a faulty signal from the torque converter clutch pressure control due to failing transmission or electrical issues
P0279 OBD-II Trouble Code: Cylinder 7 Injector Circuit Low
P0279 P0279 code definition Code P0279 is stored by the PCM when it experiences a low-voltage situation that involves the fuel injector for the number seven cylinder. What the P0279 code means Basically, this code means that one of your...
B1943 OBD-II Trouble Code: Airbag Crash Sensor #1 Short to Ground
B1943 means there is a discrepancy in the voltages to two terminals in the airbag circuit, likely due to an open circuit in a sensor.

Related questions

Van jerks, engine loses power, no acceleration - 2008 Hyundai Entourage

Hey there. A good start would be to have the car scanned to see what code has set in the computer and turn the Check Engine Light on. Your problem could be many things, from a problem with the drive-by-wire...

Hi Patrick my car has the code p1090 coming out I got the part and wanted to know what else I should look out for in my car and to

You should go ahead and replace the actuator first and then clear the codes and road test to see if the system operates correctly and if the code returns then you may have to have further diagnosis of the electrical...

Does a chevy colbat have 2 knock sensors?

You only have one sensor on this engine. If the P0327 trouble code continues then have the engine checked to see if you have an engine knock or the fuel you are using is below 87 octane, causing the engine...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com