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What Some Warning Lights & Engine Codes Really Mean

Nothing can ruin an enjoyable cruise faster than the surprise illumination of dash warning lights. Aside from running low on fuel or air pressure in the tires triggering an alert, there may or may not be much to worry about. Usually, when the check engine light pops up out of nowhere, the natural next symbol that comes to mind is “$”. But before you start sweating and stressing out, just take a deep breath, and remember—these trouble lights are meant to give you the soonest heads up of an issue that could have a simple, inexpensive solution IF addressed in a timely manner and not left to worsen over time. Let that last point sink in, and let’s keep rollin’.

“Out of sight, out of mind” is an all-too-familiar “fix” for dash lights. With the ability to plug in a code scanner and “clear” trouble lights, a lot of truck owners think that turning a light off cures whatever is going wrong underneath the hood or anywhere else that could pose a problem from bumper to bumper. Code scanners are extremely helpful—don’t get us wrong. They are great for helping pinpoint the exact code or problem that makes the dash light pop up, but they should be used as diagnostic tools and not as an off switch.

Instead of sweeping the problem under the rug, understand why the lights on your later model Chevy and Ford truck’s dash are illuminating and what the heck the lights even mean. If you haven’t taken a good look at your gauges and examined all of the symbols, they can be a bit confusing and read like some weird alien language; it must be tough to create a single symbol that represents a major system of your truck. Some of them are familiar since they haven’t changed much over the years and actually make visual sense at first glance. Others, especially the ones that correspond to more modern conveniences, can be a little trickier to understand.

With increased on-board functions and safety features, there are bound to be more problems with all those factory-installed bells and whistles. So when your dash starts lighting up like a Christmas tree, you’ll have a better grip on what your truck is trying to communicate to you through all the bright symbols and indicators. While not each and every light is explained here, some of the most common and troubling dash indicators have been expanded upon to help with understanding what your truck is telling you.

COLORS

Maybe you have noticed over the years—or maybe you haven’t paid that close attention—that the colors of the indicator lights vary. The red lights usually indicate the more serious issues that you’ll want to tend to immediately, if possible. There are a combination of yellow and orange lights that will pop up every once in a while, and these are usually less urgent, but still important to address. Green (and sometimes blue) lights are the least stressful and may mean that a system is on or they’re reminders to buckle up or that one of the doors isn’t closed all the way. So when you see a symbol light up, first address what the problem is and then its severity based on its color.

THE USUAL SUSPECTS

The check engine light is the single most intimidating alert to pop up on the dash, except for the low fuel light, that always seems to pop up as soon as you pass the last gas station for miles. The engine light can mean a long list of things, from something as trivial as a gas cap that has been improperly placed back on after refueling to more serious problems like misfiring or an improper fuel mixture.

The Check Engine symbol has been given another indicating function by staying lit when there is a less urgent issue and flashing when immediate attention is necessary. If the light is blinking, turn off any unnecessary accessories that could be drawing from the engine, and decrease speed or safely pull over is possible. These simple steps can save the engine from working harder than it needs to when the light is on. Thinking of towing? Don’t do it—at least not until the problem has been accurately detected and remedied.

A Service Vehicle Soon light is different from the check engine light, as it is connected to the body control module. It detects lamp malfunctions such as headlights to taillights and turn signals, as well. Like the check engine light, it can mean a multitude of things, some of which are purely electrical communication errors within a system, or have to do with sensors that you’d never be able to guess without the help of a diagnostic tool or having a dealership or repair shop assess the issue.

You’ll find that the Battery Service warning is always red and can mean a number of things about your truck’s charging system. There could be an issue at the battery terminals, a problem with the alternator, or simply that the battery is low on voltage and needs replacement. Don’t chance driving around and making too many unnecessary stops, or else you’ll more than likely end up stranded and have to phone a friend—or AAA.

When the Temperature warning symbol lights up, you’d better pull over and pull over fast. The last thing you need is for you truck’s engine to overheat. Let the truck cool down, and check the coolant level, look for possible leaks, and make sure the fan and thermostat are operating correctly. Don’t push your truck when this light is on—consider it to be a stoplight.

The Oilcan indicator is one of the simple lights to decipher. If it stays illuminated, that means there is a lack of oil or loss of oil pressure in the system, or simply a faulty sensor. Since oil is the lifeblood of your engine, you’ll want to take a look into this ASAP by first adding oil if needed, and then have it looked at if the light doesn’t go away.

Another oil light that can illuminate on the dash is an oil change reminder. A shop will usually slap a sticker inside of the windshield with a date and odometer reading to plan the next oil change. There’s nothing too tricky here; all the indicator means is that the life of the old oil has run its course, and it’s time for another oil change service. If this is the only light you have to worry about, consider yourself lucky.

Brake symbols can mean a few things that will require your attention at your earliest convenience. Brake fluid could just be low, the parking brake could still be on or there may be an issue with the truck’s ABS system (which should have its own light on the dash, but if it doesn’t, do take notice to the general brake light). You don’t want to chance not having properly functioning brakes, so this is one of the sensitive lights to address.

Modern vehicles are now equipped with a Tire Pressure Monitoring System (TPMS) at each tire that will alert when inflation pressure dips low. These sensors can sometimes be overly sensitive and become annoying with the alerts on the dash. When the light illuminates on the dash, add some air to the tires to the suggested pressure level. If you’ve recently swapped out the factory wheels and tires with aftermarket sets, it’s suggested to install the factory sensors to the new wheels. If not, be prepared for the TPMS light to be on at all times, and make it a point to eyeball tire inflation levels like we used to do it in the “old days.”

Traction Control, which helps prevent wheels from spinning on slippery surfaces, will automatically engage and the light on your dash will appear when your wheels start to slip. Turn off Traction Control if stuck in mud or snow and need to rock the car, or when you want to light up the rear tires and make a smoke show.


We break down the most common Chevrolet truck engine codes and show you how to check them.

When retrieving Chevy trouble codes with an OBD II scan tool, proceed as follows:

1. Connect scan tool to the 16-pin data link connector (DLC) located underneath the steering column. The connector may have a removable cover.

2.Turn the ignition on.

3.Follow scan tool manufacturer’s operating instructions to access the Diagnostic Trouble Codes (DTC’s).

Remember, these are manufacturer specific codes only. Refer to a Generic OBD II code list for definitions on all other Chevy diagnostic trouble codes.

  • P1190 Engine Vacuum Leak
  • P1191 Intake Air Duct Air Leak
  • P1218 Injection Pump Calibration
  • P1257 Supercharger System Overboost
  • P1258 Engine Coolant Overtemperature – Protection Mode Active
  • P1260 Last Test Failed SCC Or Theft Detected, Vehicle Immobilized
  • P1286 Accelerator Pedal Position
  • P1324 Crank RPM Too Low
  • P1399 Wheel Speed Sensor
  • P1408 Intake Manifold Pressure Sensor Circuit
  • P1409 EGR Vacuum System Leak
  • P1460 Cooling Fan Control System
  • P1483 Engine Cooling System Performance
  • P1500 Starter Signal Circuit
  • P1501 Vehicle Speed Sensor Circuit Intermittent
  • P1528 Governor
  • P1544 A/C Refrigerant Condition Very Low
  • P1584 Cruise Control Disabled
  • P1632 Theft Deterrent System-Fuel Disabled
  • P1695 Remote Keyless Entry Circuit Low
  • P1795 CAN Bus-Throttle Body Position
  • P1812 Transmission Over Temperature Condition
  • P1814 Torque Converter Overstressed
  • P1871 Undefined Gear Ratio
  • P1891 Throttle Position Sensor

DIESEL TRUCKS

Gasoline drivers might get thrown off right away by additional symbols that diesel users are used to. Since the fuel system is dramatically different, there are issues that uniquely belong to diesel engines.

One symbol that will pop from time to time is the Glow Plug light, which indicates that the engine’s glow plugs are in the process of warming up. It is suggested to wait until this light turns off before attempting to start the engine. Duramax engines are equipped with glow plugs, while Cummins engines have grid heaters. Both can be started without these components being engaged, but the engine will start much easier in the cold with them primed and ready to go.

The DPF (diesel particulate filter) light, which corresponds to the diesel particulate filter, will illuminate when the filter fails its test and must be serviced. Introduced in 2007, this filter was designed to regenerate, or clean itself. If the system fails to do so, it must be done manually to prevent a reduction in engine power. If this red light comes on, it may also trigger the check engine light along with it.

Diesel exhaust fluid (DEF) creates a catalytic reaction that extracts harmful particles from the exhaust. When this fluid is low, the corresponding light may appear on the dash, telling you to add fluid to the system, or that the fluid that is in the system is contaminated. In that case, the fluid must be replaced.

Water in the fuel is also a big problem that diesel drivers face. There are multiple versions of symbols that translate this problem on the dash, but they will all alert to the same issue. A filter is designed to separate water from diesel fuel, when water sneaks its way into the fuel, you should see this alert, which will most likely warrant the changing of the fuel filter and draining of the fuel tank.

Note: All makes and models function differently, and use variations of symbols that pretty much mean the same things. Whatever you drive, you should be able to detect the problem by either referring back to this handy issue of your favorite magazine, flipping through your truck’s owners manual, making a pit stop at a local dealership, or spending some time with Google.

 

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