Generic OBDII P Codes P0500-P0599

Learn the code definitions and most common causes for Generic OBDII P Codes P0500-P0599

This post lists the most common trouble codes in the OBDII P Codes P0500-P0599 category. These are Vehicle speed and Idle System trouble codes. Start by reading the most common codes and causes and then refer to the code chart at the end of the post for official code definitions.

I’ll start by discussing the most common Trouble codes in this group, along with the most common causes of those codes. If you’d like a full list of the codes in this group, scroll to the bottom of this article.

How to find your P Codes P0500-P0599 definition

There are 133 500-series codes. There are several ways to find the code definition in the chart below.
1) Enter the trouble code in the search box. That’s the fastest way
2) If you’d like to scroll all the codes, change the Number of entries to show on the page in “Show Entries” box. Click NEXT or PREVIOUS at the bottom right of the table

This graphic shows the three ways you can navigate the refrigerant chart: 1) Increase the number of entries, enter the year of your vehicle in the search box, or scroll the chart using the next/previous buttons at the bottom of the chart

The most common causes of OBDII P Codes P0500-P0599

P0504 Brake Switch “A”/”B” Correlation is becoming a more common code

In the old days, the brake switch just turned on the brake lights. But in late-model cars, it’s used to operate the shift interlock solenoid that prevents you from starting the car in any gear other than Parker Neutral. It’s also used to operate start-stop systems, so it’s no longer a simple on-off switch. Start-stop systems need to know when you’re beginning to release the brake pedal so it has enough time to restart the engine. Because of this, modern brake pedal switches are built with potentiometers that report a varying signal as you apply and release the brake pedal.

Symptoms of a bad brake switch

• You have no brake lights when pressing the brake pedal
• Your brake lights stay on when your foot is off the brake
• Your cruise control doesn’t work
• You can’t shift out of park after starting your engine
• Your engine stalls when you brake

Fix for P0504 Brake Switch “A”/”B” Correlation

You can test the switch using a multimeter and the shop manual specifications but in most cases when this code shows the brake switch is bad. Purchase a new switch and follow the shop manual instructions for installing and adjusting the new switch.

P0555-P0559 Brake Booster Pressure Sensor Circuit Codes are becoming more common

Brake booster pressure sensor

Carmakers use an electric vacuum pump on small displacement engines to provide vacuum for the break vacuum booster component. Small displacement engines can’t produce enough manifold vacuum to operate the vacuum booster fully. The speed of the vacuum booster is determined by the brake booster pressure sensor installed in the vacuum line between the met engine and the brake booster. If the vacuum pump can’t provide enough vacuum, it will set any one of these brake booster pressure sensor circuit codes.

brake booster electric vacuum pump

Diagnosing a brake booster pressure sensor trouble code

To diagnose a brake booster pressure sensor trouble code you’ll need a multimeter, a wiring diagram and the specifications from a shop manual.

Start by checking the condition of the vacuum line into and out of the pressure sensor. Look for cracks and replace lines that have any abrasions or cracks. Next, check for the values shown in the shop manual. If the values you find are out of specification replace the sensor.

P0521-P0524 Engine Oil Pressure Sensor/Switch Circuit/Range codes are becoming more common

Carmakers use an engine oil pressure sensor along with an oil temperature sensor to properly operate both the variable valve timing system and the variable speed oil pumps used in modern engines. Unlike the old oil pressure sensors that were simply an on off switch, the newer sensors report varying voltage based on actual oil pressure.

The most common causes of a P0521 trouble code

• Low oil level
• Dirty oil or sludge that’s clogging oil passages
• The wrong oil filter that’s restricting oil flow
• A bad oil pressure sensor
• A bad oil pump
• A damaged wiring harness or electrical connector to the oil pressure sensor

Diagnose a P0521 code

Start by checking the oil level. Off if necessary. Next, double-check that you’ve installed the correct oil filter. If those items check out, rent an oil pressure gauge from any auto parts store. Then, remove the oil pressure sensor and install a mechanical gauge. Start the engine and check the oil pressure and compare it to the specs in the shop manual. If the pressure is good, the sensor is bad. Replace the sensor.

P0531-P0539 AC refrigerant Pressure Sensor Circuit Low, High, Range Performance are common codes that indicate low or high refrigerant pressures

Carmakers have long used refrigerant pressure sensors, but they’ve been used to allow or inhibit AC compressor operation. On late-model cars they’re used to help the climate control systems operate more efficiently.

Diagnose an AC Pressure Sensor Code

The ac refrigerant pressure sensors rarely fail. When they report any of these trouble codes the cause is usually a low refrigerant level or a refrigerant over-charge condition. To diagnose these codes, connect a manifold gage set to the high and low ports on the AC system. Operate the AC system on Max Recirculate and compare the readings to a normal pressure reading chart

P053A-P053C Positive Crankcase Ventilation (PCV) Heater Control Circuit codes are becoming more common

The positive crankcase ventilation system is used to route crankcase blow-by back into the intake manifold so it can be burned. On late-model cars with direct fuel injection, the blow-by contains more moisture than in port-injected engines. That has caused a problem in extremely cold weather, where the humid blow by freezes in the PCV valve. To combat this problem carmakers have installed heaters inside the PCV valve to prevent ice buildup.

If the PCV valve heater fails you’ll see one of these trouble codes:

P053A Positive Crankcase Ventilation Heater Control Circuit /Open
P053B Positive Crankcase Ventilation Heater Control Circuit Low
P053C Positive Crankcase Ventilation Heater Control Circuit High

Diagnosing a P053A-P053C code

Start your diagnosis by checking the wiring harness and electrical connector to the PCV valve heater. The PCV valve heater is a high failure rate item on some vehicles, so you’ll most likely wind up replacing the PCV valve and heater.

P0597-P0599 Thermostat Heater Control codes are very common, especially on GM vehicles

Electrically heated thermostat and thermostat housing

Carmakers use a thermostat heater to respond faster when the driver calls for more power.That creates a rapid rise in coolant temperature. Older thermostats without a heater don’t respond quickly to rapidly changing temperatures . By installing a heater and monitoring engine coolant temperature, the ECM can immediately provide power to the thermostat heater , forcing it to open quickly and allow more coolant flow.

The most common causes of P0597-P059 codes

In most cases, especially on GM vehicles, the plastic thermostat housing fails, causing these codes along with a large coolant leak. On other vehicles, the heater itself may fail. The fix is to replace the entire thermostat housing.

©, 2024 Rick Muscoplat