Vehicle diagnostics aren't always straightforward. Sometimes a vehicle arrives with symptoms that seem to point in one direction, only for testing to reveal a completely different root cause.

Recently, we worked on a 2019 GMC Acadia with 151651 miles that came in with complaints of hesitation, bucking while driving, and a noticeable lack of power. What initially appeared to be an engine performance issue ultimately led us down a different diagnostic path.

The customer reported that the vehicle was hesitating and bucking during acceleration. A scan of the vehicle revealed several diagnostic trouble codes:

• P0700 – Transmission Control Module Requested MIL Illumination
• P0716 – Input Speed Sensor Performance
• P0717 – Input Speed Sensor No Signal
• P219A – Air/Fuel Ratio Imbalance

At first glance, the P219A code and drivability concerns suggested there could be an engine-related issue contributing to the problem.

During our inspection, we noticed fuel trim data indicating an air/fuel imbalance. The vehicle also exhibited a rolling idle, and we discovered that a camshaft solenoid had been replaced by another repair facility just one day earlier.

Because of the recent repair work, we carefully inspected:

• Intake manifold connections
• Vacuum lines
• PCV system components
• Wiring harnesses and connectors
• Intake gaskets and sealing surfaces

We also found oil present inside the intake manifold and portions of the PCV system, which warranted further inspection.

After cleaning components, inspecting the intake system, reinstalling the manifold with properly cleaned gasket surfaces, performing an idle relearn procedure, and completing injector balance procedures, the vehicle ran significantly better in the service bay.

At that point, it appeared we may have addressed the concern.

However, during the road test, the symptoms quickly returned. When stopped at a traffic light, the vehicle struggled to accelerate. There was virtually no takeoff power, and the transmission's Drive indicator began flashing. Most importantly, the P0717 code immediately returned. This shifted our diagnostic focus away from the engine and toward the transmission.

The P0717 code indicates that the Transmission Control Module is not receiving a signal from the transmission's Input Shaft Speed Sensor.

This sensor plays a critical role in transmission operation. The control module uses its signal to determine:

• Shift timing
• Gear ratios
• Torque management strategies
• Overall transmission performance

Without a valid input speed signal, the transmission may enter a protective mode that significantly reduces vehicle performance.

Using scan tool data, we monitored:

• Engine RPM
• Transmission Input Shaft Speed
• Transmission Output Shaft Speed

With the engine running, the transmission input shaft speed remained at zero RPM.

The output shaft speed reading was expected to be zero while stationary, but the input shaft speed should have been providing a signal.

Further testing revealed:

• Wiring and external connectors appeared intact
• Grounds tested properly
• The input speed sensor showed no visible physical damage
• The reluctor wheel did not show obvious signs of failure during visual inspection

Following GM's diagnostic procedures, the evidence pointed toward either:

• A failed input shaft speed sensor
• An internal valve body-related issue affecting the sensor circuit

One factor that supported our diagnosis was parts availability and failure history. After speaking with a local Chevrolet dealership, we learned that they regularly stock and sell a significant number of input shaft speed sensors compared to valve body assemblies. In many cases, high dealer inventory and frequent part movement can indicate a commonly encountered failure. Combined with our test results, replacing the input shaft speed sensor became the most logical next step before considering more extensive transmission repairs.

Upon removing and inspecting the newly installed input shaft speed sensor, we discovered that the tip of the sensor had become physically damaged. This damage was not caused by the new sensor itself. Instead, it indicated that an internal transmission component had made contact with the sensor. The most likely cause was internal transmission failure resulting in damage to the reluctor assembly or related rotating components that interact with the input shaft speed sensor. At that point, the transmission had progressed beyond a sensor failure and into internal mechanical damage.

Due to the internal transmission damage, replacement of the transmission assembly was recommended. While the initial fault codes pointed toward a speed sensor issue, the damaged replacement sensor confirmed that the underlying problem was much more severe. The failed sensor was actually a symptom of a larger internal transmission failure.

At Bolt Auto Care, we know that keeping up with regular maintenance isn’t always easy — life gets busy, schedules get packed, and your car often ends up at the bottom of the to-do list. That’s why we created something new just for you — the Bolt Care Plan.

This exclusive membership is designed to make car care simpler, smarter, and more affordable for drivers who want peace of mind and great service all year long.

The Bolt Care Plan is our brand-new membership program built to reward loyal customers and make maintenance stress-free.

As a member, you’ll enjoy exclusive savings, priority scheduling, and added perks that make every visit to Bolt Auto Care even better. Think of it as a VIP pass for your vehicle — giving you confidence that your car is always in top shape without breaking the bank.

Here’s what makes the Bolt Care Plan worth it:

✅ Exclusive Discounts – Save money on oil changes, repairs, and maintenance services every time you visit.

✅ Priority Service – Members move to the front of the line! Enjoy faster turnaround times and preferred scheduling.

✅ Maintenance Reminders – Never miss an oil change or inspection again — we’ll keep you on track.

✅ Member-Only Perks – Get access to special offers, seasonal deals, and occasional freebies available only to Bolt Care members.

Regular maintenance is the key to keeping your car running smoothly and avoiding costly repairs down the road. With the Bolt Care Plan, you’ll:

• Save on essential services you’re already using

• Stay ahead of problems before they become expensive

• Get personalized attention from a team that truly cares about your car

In short — you’ll spend less time worrying and more time driving with confidence.

Becoming a member is quick and easy! Simply stop by Bolt Auto Care in Gainesville or contact our team to learn more about the membership options available.

Whether you’re a longtime customer or it’s your first visit, we’d love to help you take advantage of everything the Bolt Care Plan offers.

Join the Bolt Care Plan today and enjoy the peace of mind that comes with knowing your car is getting the best care — every time.

⚡ Because at Bolt Auto Care, we don’t just fix cars — we care for them.

• Reduced power output: As temperatures drop, the chemical reactions inside your battery slow down, meaning it produces less energy.

• Harder starts: Cold oil and sluggish fluids make your engine harder to turn over, putting extra strain on the battery.

• Older batteries struggle most: If your battery is more than 3 years old, cold weather may expose its weakness.

1. Inspect regularly: Look for corrosion on terminals and ensure cables are tight.

2. Test your battery’s strength: A quick test can show how much life it has left.

3. Keep it clean: Dirt and corrosion can drain power.

4. Limit short trips: Cold starts combined with short drives don’t give your alternator enough time to recharge the battery.

5. Replace before it fails: Don’t wait for a dead battery—swap it out when testing shows it’s weak.

At Bolt, we offer:

• Free battery checks to measure voltage and health

• Professional cleaning of battery terminals

• Quick and affordable battery replacement if needed

We’ll make sure your car starts strong, no matter how low the temperature drops.

In North Texas, colder mornings can drain even a healthy battery. If your car is slow to start, don’t ignore it. It’s often the first sign your battery is on its way out.

👉 Stop by Bolt Auto Care in Gainesville for a free battery check before the cold weather really sets in. It’s fast, easy, and can save you from a winter morning headache.

• Air contracts when it gets cold. For every 10°F drop in temperature, your tires can lose about 1–2 PSI (pounds per square inch).

• Even healthy tires are affected. This means you might start your car on a chilly morning and see that TPMS warning, even if nothing is wrong with your tires.

• Low pressure = unsafe driving. Underinflated tires wear faster, reduce fuel efficiency, and increase the risk of a blowout.

1. Check your tires with a gauge. Don’t rely only on the light—use a tire pressure gauge to confirm the actual PSI.

2. Fill to manufacturer’s specs. You’ll find the recommended pressure inside your driver’s side door or in your owner’s manual.

3. Don’t ignore it. Driving with low tire pressure can damage your tires and affect your safety.

At Bolt, we know how unpredictable North Texas weather can be. Swing by our Gainesville shop, and we’ll:

• Check your tire pressure for free.

• Inspect your tires for leaks or damage.

• Reset your TPMS light after adjustments.

We’ll make sure your car is ready for those chilly mornings and safe for your daily drive.