P0606 Diagnostics Trouble Code – Know the Meaning, Causes, and Symptoms

No motorist or car owner wants to be stranded in the middle of nowhere. But, in any case, some car problems are unavoidable. It’s only a matter of time. When an unforeseen car breakdown happens, one is faced with finding the appropriate and efficient means of rectifying the problems.

Sometimes, the cause of the problem may be minor and easy to fix. Other times, it may be an extensive repair and challenging to track the root cause because the issue can come from several system components. Fortunately, an OBD scan tool makes diagnosing process easier and fixing faster.

If the scan tool finds that the car computer has stored the P0606 fault code, it means there is a problem related to the powertrain control module (PCM) or the engine control module (ECM). This is a severe case that can keep you on the road.

Here, the Rx mechanic team of experts will discuss the causes, symptoms, and how to diagnose and fix the P0606 diagnostic trouble code. But first, let’s see the meaning of P0606 on Honda and other cars of different models and brands.

p0606 toyota

What does error code P0606 mean?

A logged P0606 error code means the PCM has an operational problem. This shows that the powertrain control module is not working how it should. Sometimes, the fault code P0606 on VW and other car models means the engine control module is dead. However, the issue may arise from shortened or open ECM wiring harness.

To better understand the P0606 code, you need to understand what the PCM does. The powertrain control module is the car computer or car’s brain. It collects signals, reports, and readings from several car sensors and system components. It uses these data to adjust or direct other system components for a seamless vehicle operation.

In addition, the engine control module communicates with other system modules to offer a streamlined driving experience. For example, the MAF sensors tell the car computer the amount of oxygen entering the engine. The car computer then adjusts the oxygen (if needed) or throws a fault code and a check engine light to notify the driver of an imminent issue.

Likewise, if the car computer throws P0606 on Ford Fiesta or your respective car model, it means it has diagnosed itself and sees that it is inoperable. Because it oversees several system components, several components will malfunction as well.

What is the symptom of error code P0606?

Several symptoms accompany the P0606 diagnostic trouble code. Some of the signs will cause unnerving and frustrating driving situations. The common symptoms of a P0606 error code are engine warning lights, random cylinder misfiring, hard starting, engine stalling and hesitation, rough idling, etcetera.

Here are the common signs you should watch out for.

Check engine light

Whether you have a P0606 on Ford Focus or P0606 on Chevy, the engine control unit will project a warning light on the dashboard. This is to notify the driver of an underlying issue. So, once you have this light, diagnose your car and track the root cause of the problem.

In any case, several system component issues can cause the PCM to project the check engine light. Therefore, you can’t determine whether or not you have a registered P0606 fault code when the engine warning light pops up on the dashboard.

Increased gas mileage

Since the PCM oversees the MAF and O2 sensor that reports the air-fuel ratio, it can send too much fuel into the engine if it fails. This means frequent visits to gas stations and more money.

Random misfire

Several factors can cause random misfires. However, this mainly occurs when the fuel injectors fail to deliver adequate fuel into the cylinders. This also causes ‘engine running lean or rich.’

As reiterated above, the car computer controls several system components. And the fuel delivery system is no exception. As a result, a logged P0606 on Nissan or other car models can cause random misfires.

Rough idle

Like engine misfires, a malfunctioning PCM will compromise the smooth operation of several system components, leading to a rough idle. It’s quite easy to know a vehicle is running rough when you start the vehicle. You may see the RPM fluctuating up and down, or it may go below 6,000 RPM.

Several parameters like lousy spark plugs, bad MAF sensor, defective O2 sensor, clogged air filters, fuel delivery, and exhaust system issues can cause rough idle.

Other potential symptoms are:

  • Intermittent stalling
  • Engine not cranking
  • Improperly timed or hard shift
  • Erratic fan actuation
  • Crank without start.
  • ABS light illuminates the dashboard.

What Causes error code P0606?

There are quite a few possible causes of P0606 on Lexus or your respective car. In any case, you must conduct proper diagnostics. Else, you’ll wrongly replace expensive components. Here are the few causes of a P0606 code.

  • Corroded, broken, or frayed PCM wiring harness
  • Defective Controller Area Network (CAN) bus communication
  • Broken, frayed, or corroded powertrain control module connectors
  • Lousy powertrain control module ground circuit.

How serious error code P0606 is?

The powertrain control module (PCM) or engine control module (ECM) oversees and regulates the electrical and engine components. Your car cannot function properly without a good PCM.

In some cases, the vehicle will crank multiple times before coming on and may even die suddenly when stopping or slowing down. For this reason, a P0606 on Toyota or any car model is a severe case and should be treated on time.

Common P0606 diagnosis mistakes

Auto mechanics hardly misdiagnose the P0606 error code because the fault is pretty simple to diagnose. It mostly means the PCM is bad and needs replacement or reprogramming.

In any case, the common mistake is not diagnosing the vehicle to pull the registered error code. Instead, you repair the symptoms of a lousy PCM. Several faulty components can project one symptom when they fail. Therefore it is important first to diagnose the vehicle with a scan tool and confirm the registered error code. The next mistake is not checking the PCM wires and connectors before replacing the PCM.

How to diagnose

If you’re a DIYer and want to track the root cause of a P0606 error code and fix it at home without wrongly replacing parts, this is the right guidance you need. Kindly note that this is not a beginner diagnosis. It is an intermediate diagnosis. The diagnostics procedure requires some basic hand tools and a scan tool. It could be labor intensive and time-consuming task for DIYers.

Tools and Items needed.

  • Scan tool
  • Basic hand tools
  • Multimeter
  • Your car-specific repair manual

Step 1: Diagnose the vehicle

Grab your scan tool and locate the car’s OBD port. Next, plug the scan tool into the OBD port and see if there are other registered fault codes. If there is, write it down because you may have to trace the root cause.

Step 2: Examine the power connections

Grab your multimeter and inspect the ignition and battery power connections to the powertrain control module. If there’s no power on one or any of these, examine the fuse for circuits. Then, carry out a resistance test to test the integrity of the circuit.

Step 3: Examine the ground connections

Examine the engine control module ground connections. Carry out a resistance test to see if you have an open circuit if you can’t find the ground where it should be. Repair or replace bad wires.

If the powertrain control module power and ground connections are good, consider replacing the PCM.

How do you fix P0606?

Whether you have P0606 on Peugeot or P0606 on Cummins, you can fix it by doing one or more of the followings.

  • Replacing or repairing faulty PCM grounds
  • Repairing or replacing corroded or broken PCM connectors
  • Replacing or repairing frayed or broken ECM/PCM wires.
  • Replacing a bad powertrain control module.

Approx. Repair Cost

Factors like bad PCM, frayed ECM wires, and bent or damaged powertrain control module connectors can cause the P0606 fault code. Hence, it is impossible to say the exact repair cost without proper diagnostics.

If you choose to have a mechanic track and fix the culprit, he’ll start with an hour of diagnostics. Most repair shops charge $75 to $150 per hour. After the diagnosis, they can give an accurate estimate to repair the P0606 code issues. If you have the repair shops that will not charge you for diagnostics around you, do the job.

When dealing with a P0606 diagnostic trouble code, you’ll need one or all of the following to fix the problem. The estimated prices below include the parts and service fee to rectify the underlying issues.

  • PCM wiring or connector repair/replacement $100 to $1000
  • Replace the powertrain control module for $800 to $1300.

car control module


Q: Can you drive with code P0606?

While the symptoms of a P0606 error code vary, it is a severe case. You can sometimes drive with this code for a while without a total breakdown. However, track and fix the root cause once you notice it because it can leave you stranded in the middle of nowhere.

Your car may suddenly shut down on the highway because the PCM is malfunctioning. Of course, you know what this means. Driving with a P0606 puts your life, the passengers, and other road users at risk.

Q: Where is the PCM fuse located?

Different cars come in different designs. Therefore, it is hard to say where the PCM fuse is located in all vehicles. In any case, the majority of the PCM fuses are located in the fuse box in the engine bay. In most vehicles, the fuse box is located on the driver-side, close to the firewall.

There may be more than one PCM fuse in a car. For instance, the KIA Optima has two ECM fuses. The diagram on the fuse cover indicates them as ECM 3 and ECM 4.

Q: Who can reprogram my PCM?

Reprogramming a PCM is an advanced task. Car dealerships mainly do it, but local repair shops or individuals with a grounded auto repair experience can reprogram the engine control module (ECM), powertrain control module (PCM), and other programmable modules.

Q: How do you test a PCM?

If you suspect you have a bad PCM, you would want to test it to see if it is the culprit or not. Here are a few ways to test PCM.

Visual inspection

Carry out a visual inspection of the PCM wiring and connectors. Also, check the battery terminals and ensure there is no rust. Clean any rusted components and tighten loose connections.

Examine the battery

The next step is to check the battery voltage. The battery volts should be 12.6v when the engine is off and 13.7 when the engine is running. If you have lesser volts on the battery, replace or charge the battery. After that, test the battery again. Again, the battery must be fully charged before moving to the next level.

Scan the vehicle

If there’s no rust and the battery is fully charged, get a scan tool and scan the vehicle. This will help you to track the root cause easily. If the PCM is bad, the scan tool will pull error codes like P0606, P0603, P0113, and U0100.

Examine sensors and wiring

Here’s where things get tricky. First, perform a visual check on all the sensors and wires that link to the PCM. After that, check them with a multimeter and ensure power and ground connections are okay.

Replace the PCM

If everything is good and the problem persists, swap or replace the PCM with the correct one. The new PCM has to be the same make, model, and year. If the performance improves, you have a bad PCM.

Q: How much does a new module cost?

Factors like manufacturers, engine size, and performance affect the price of a new engine control module. However, the average cost of a new module is between $250 and $350. This is an estimated price, meaning your specific car engine control module price can be higher or lower than the average price.

Final Words

The P0606 diagnostic trouble code shows the powertrain control module (PCM) is malfunctioning. This could mean you have a bad powertrain control module, frayed or burnt PCM wires, or bent or broken PCM connectors.

This is a severe case that can keep you frustrated on the road. Therefore, tracking and fixing the culprit as soon as possible is important. This article has provided a simplified guide on how to diagnose and fix the problem. However, this is not a beginner task. Consult an experienced mechanic if you’re not grounded with auto repairs.

Osuagwu Solomon

Osuagwu Solomon is a certified mechanic with over a decade of experience in the mechanic garage, and he has over five years of experience in the writing industry. He started writing automotive articles to share his garage experience with car enthusiasts and armature mechanics. If he is not in the garage fixing challenging mechanical problems, he is writing automotive repair guides, buyer’s guides, and car and tools comparisons.

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