How to Confirm a Failing PCM Using Diagnostic Tools

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Problems with the Powertrain module or PCM in your vehicle can be difficult to understand. But with the right diagnostic tools, you can have the problem fixed in no time.

• While Suspected Often, Actual PCM Failures Are Rare
• It All Begins with the Right Scan Tool
• The Innova Three-Step Diagnostic Approach
• Life In Random: Guessing Will Always Cost More
• What’s Next? — Using the Innova 5610 to Diagnose Your Vehicle Malfunction
• FAQs: Confirming a PCM Failure with Diagnostics Tools

Certain parts and components in modern vehicles tend to take the blame for operational problems. Visit a forum, an auto repair site, or talk to someone with basic maintenance knowledge, and they might point to a specific part as the core of your issue. For example, the Powertrain control module, or PCM, is commonly targeted as a culprit. It’s also one of the most expensive parts in your vehicle, and the most misdiagnosed.

Lots of people jump to the “your PCM is bad” conclusion, which, on the worst day, is right, but on most days is probably wrong. It’s tempting to blame the computer, but before replacing anything, especially such an expensive part, it makes sense to rule out potential alternatives first.

You cannot do that empty-handed, as is the case with most repair and maintenance tasks. You need the right tool, specifically the right scan tool. Our recommendation for this is the Innova 5610. Namely, that’s because it offers pro-level diagnostics with no gimmicks and no subscriptions.

Let’s explore why the 5610 is such a good tool for PCM failures and the related diagnoses.

While Suspected Often, Actual PCM Failures Are Rare

You may know this, or you may not, but most modern vehicles are filled with separate computers. It’s not one central computer, in other words, but several, separate systems working together to keep you informed and keep your vehicle operational.

The Powertrain Control Module, or PCM, is one such computer. Its purpose is fairly straightforward — it’s in the name, after all. The PCM controls all components and systems related to the Powertrain. It’s the brains behind the engine and the transmission. Don’t confuse the Powertrain module with the Engine Control Module or ECM, they are different.

It’s not common for any computers to malfunction or break down in a vehicle, and that’s true of the PCM, as well. But it can and does happen, so we will never say never.

Some Common Symptoms of a PCM Failure

Because it does happen, it helps to know what symptoms to look for when a PCM failure is the root cause. More importantly, this will also illustrate how there’s an overlap between other components and mechanical failures.

Vehicle issues, in general, share a lot of the same symptoms, which can make diagnosis challenging — precisely why we recommend a reliable scan tool.

Here are the symptoms associated with a PCM failure:

• The check engine light is on.
• Poor vehicle performance.
• Difficulty starting the vehicle.
• Increased emissions, smog, or smoke.
• Decreased fuel economy.
• Shifting problems or gears that stick.

Again, PCM failures are not common. It’s more likely that these symptoms, if you are experiencing them, are caused by something else.

When a PCM does fail, it may show signs such as:

• Random misfires with no mechanical cause.
• No communication with one or more sensors.
• Inconsistent fuel trim or timing data.
• Modules that won’t respond during scan attempts.

But these issues are not always directly related to the powertrain module. They can also be caused by:

• Corroded grounds
• Failing ignition coils
• Faulty sensors or relays
• Bad connections in the CAN bus network

Which brings us full circle to the original question. How do you actually know it’s the PCM, and how do you diagnose the problem?

It All Begins with the Right Scan Tool

Scanners essentially read diagnostic trouble codes (DTCs) from the vehicle’s computer to help discern malfunctions and errors. But realistically, you need a scanner that does more than just pull those codes. To confidently confirm or eliminate the PCM as the core issue — or any other components, for that matter — you need additional diagnostics data.

Your tool must be able to:

• Access all available control modules, not just the ECM.
• Display live data from multiple sensors at once.
• Confirm whether modules are communicating properly.
• Check for manufacturer-specific codes that basic readers miss.

At its price range, the Innova 5610 is one of the few tools that can give you the appropriate visibility. It provides pro-level diagnostics at a fraction of the cost.

But how do you use the 5610 to find the real culprit?

The Innova Three-Step Diagnostic Approach

We highly recommend using a relatively simple, three-step method:

1. Scan All Systems

Step one is to run a full network scan. You’re not just looking at the engine module or PCM, but for system-wide flags. Pay attention to “no communication” messages or missing module reports. That signals something is wrong elsewhere.

2. Compare Data Streams

Use live data reported through the tool to check for statistical values that don’t change, don’t correlate with regular operation, or just flat-out don’t make sense. A great example is a scanner showing the throttle position stuck at 0% while you’re pressing the pedal.

3. Validate Grounds and Power

If the tool shows that the PCM is not responding, use it to check voltage inputs at key fuses or data points. It may not actually be a “dead” PCM; it may not be receiving power.

If any of these steps reveal inconsistencies, then — and only then — should you start considering a full PCM replacement.

Life In Random: Guessing Will Always Cost More

Replacing a PCM costs anywhere from $800 to $1,500 when you need programming. But if you misdiagnose and skip right to replacement, a new PCM may not even fix the underlying issue. Not only would you be wasting all of that money, but you may still run into problems using the vehicle afterwards.

You need to make a diagnosis that’s backed by data — real, tangible values. And that’s where the Innova 5610 comes into the equation.

It can:

• Catch sensor issues before they mimic PCM faults.
• Confirm if other modules are communicating properly.
• Reveal if live data supports the theory of failure.

In addition, when paired with the RepairSolutions2 app, you can receive vehicle-specific repair guidance based on the make and model. It can even recommend parts and where to get them, along with delivering step-by-step repair instructions, which is vital for DIYers.

What’s Next? — Using the Innova 5610 to Diagnose Your Vehicle Error or Failing PCM

You’d like to get back on the road as soon as possible. We get it. Let’s make that happen.

If you’d like assistance diagnosing the problem with your vehicle, be sure to reference our PCM diagnostics checklist while using the 5610. Alternatively, if you’re not sure which scanner gives you the visibility and features you need, see our guide on why pros use the Innova 5610 for PCM diagnostics.

If you’re ready to get started, order the Innova 5610 for yourself now.

FAQs: Confirming a PCM Failure with Diagnostics Tools

After reading the guide, you may have some more questions about PCM failures, advanced diagnostic tools, and Innova’s products, in general. We’ll do our best to answer them here.

How do you know for sure a PCM is bad?

As you’ve undoubtedly surmised, there are many symptoms related to a failing or bad PCM. And that’s in addition to a check engine light showing up. So, how do you know that the PCM is the real culprit?

Unfortunately, there is no telltale sign, meaning there’s no single flag or symptom you can point to directly to know for sure. Diagnosing a PCM failure requires a host of information so you can make a contextual decision.

Can the Innova 5610 help you discover a PCM failure?

Yes, the Innova 5610 reads and reports the precise data you’ll need to discern if the PCM is bad or if there’s another component that’s causing the issue.

To confidently confirm or eliminate the PCM as the core issue, you need additional diagnostics data, such as access to all available control modules, live data from operating sensors, communication status and responses, and manufacturer-specific error codes that may show up. The 5610 provides all of this and more.

Why is the PCM commonly blamed for engine issues?

Despite being uncommon or rare, a PCM failure essentially casts a wide net when it comes to engine and performance issues. Everything from poor performance, decreased gas mileage, and excess emissions can be signs of a PCM problem. Engine not starting? Yeah, that could be the PCM, too.

Once you see just how much the PCM can cause, you’ll immediately understand why it’s usually a scapegoat.

What about other engine or component failures? Is a scanner tool necessary?

While we can’t say for certain whether you’ll need a scan tool to understand the problem, since it varies from issue to issue, we can say definitively, you’ll be better off. That’s because advanced tools like the Innova 5610 go beyond the error codes. They give you real-time and live data of the engine and its parts in action. That way, you can diagnose electrical anomalies, component failures, emergency shutdowns and other concerns.

In short, a reliable scanner tool is a must-have for any automotive toolkit.

What can the Innova 5610 do that other tools cannot?

The 5610 enables full-system module scans for a clearer picture of what’s going on with the electronics. But more importantly, it offers live comparisons of multiple sensor values, CAN Bus communication fault detection, Powertrain, body and network error codes, and bidirectional system tests. Collectively, all of these functions and features help you get to the bottom of a malfunction, such as when it looks like the PCM is bad.

Interested in learning more? Learn more about This Is Why Pros Use the Innova 5610 for PCM Diagnostics.

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