AfterMarketNews Auto Care Pro AutoProJobs Auto-Video.com Brake&Frontend BodyShopBusiness Counterman EngineBuilder Fleet Equipment ImportCar Motorcycle & Powersports News Servicio Automotriz Shop Owner Tire Review Tech Shop Tomorrow's Tech Underhood Service

Second-rate parts mean second-rate results

When it comes to diagnosing a problem, one of the biggest mistakes is thinking that the problem is gone after you’ve installed a new part. I’ve had vehicles brought in countless times with the same old story attached to them. The customer will say:...

Read more...

GearWrench Launches Street Team, a New Mobile Driver Program

GearWrench, a premier hand tool brand from Apex Tool Group, has announced Street Team, a new program that gives independent mobile distributors the support of an established tool brand without the restrictions of a franchise. "Response to the program...

Read more...

AUTO 7 Named Approved Vendor For Automotive Parts Associates

Steven Kruss, president of Auto 7, which supplies Korean-made, OEM-quality automotive parts to distributors across North America, announced that Auto 7 has been named an approved vendor of Automotive Parts Associates (APA), one of the nation’s...

Read more...

Internal Engine Oil Consumption Diagnostics

Due to the variables in engine design and ­operating conditions, internal engine oil ­consumption complaints are often the most difficult to solve. In some cases, oil consumption might be more severe under low-speed operation, in other cases, high-speed...

Read more...

Hyundai Fuel System, Emissions Diagnostics

Hyundai has done a good job of improving its ­offerings over the years from both an aesthetic and mechanical viewpoint. Complemented by a strong warranty and good value, the carmaker has been able to increase its market share year over year. If you aren’t...

Read more...

Curing Volvo Manual Transmission Rattle

In an effort to increase fuel efficiency, today’s engines produce more torque so they can be ­driven at extremely low rpm. ­Reduced viscosity engine and gearbox oils, less vehicle weight and improved aerodynamics also contribute to better fuel economy....

Read more...

Servicing The Electronically Adjustable Shocks Of Full-Sized GM Trucks

Since the 2000 model year, GM has offered electronically adjustable suspension as an option on Chevy, Cadillac and GMC full-size trucks. The system actuates the valving in the shocks to control ­suspension position and body attitude. The electronic...

Read more...

Diagnosing Clutch Assembly Noises

Noise can resonate from many areas of a ­vehicle’s driveline. There are several types of noises associated with the clutch assembly. The release bearing is most often blamed for being the cause of noise when, in many cases, it is not the release...

Read more...

Making Sense Of Steering Angle Sensor Input And Data

Measuring the­ ­position angle, rate of turn and force of the steering wheel is critical for Electronic Stability Control (ESC) systems. Scan tools call these Steering Angle Sensors (SAS) and typically display the information in degrees. The SAS...

Read more...

Talk To All Available Modules With Autel's MaxiDiag Elite MD802

Derived from Autel’s Professional Series tool, the MaxiDAS DS708, the MaxiDiag Elite MD802 enables the user to not only get into the OE enhanced OBD II system with mode 6 access and live data graphing, but it also allows a technician to scan the...

Read more...

Reflashing & Reprogramming Tools

In the first half of 2014, NHTSA has issued more than 15 recalls where the fix was to reflash a module on a vehicle. In the same time frame, more than 100 TSBs have also been issued where the solution is to reflash a module. These recalls and TSBs...

Read more...

Pulling Codes: An Advanced Misfire Story The Story of P0301

This article will document code P0301 — Misfire Activity on Cylinder No. 1 — a code many of you have run into, but sometimes we have case studies that are worthy of mention. Our subject vehicle is a 2007 Mercury Mountaineer. The vehicle has...

Read more...

Home Emissions Pulling Codes: The Story of Code P0456

Print Print Email Email

This article will document the ­infamous P0456 code — 0.20 leak detected. A small leak code can be the most challenging for any of us, so the following is a suggested plan of attack.
Through my research, I’ve found that all of the auto manufacturers appear to run their EVAP monitors in a certain sequence, and I have studied this in detail for GM, Ford and Chrysler vehicles. figure 1: p1495 and p1494 — check by the pcm at koeo and koer
We’ll begin our diagnostic journey with Chrysler. There is a manual that Chrysler produced some time ago that offers an engineering perspective into the operation of its Leak Detection Pump (LDP) system — Leak Detection Pump Operation and Diagnosis (Publication No. 81-170-00006). (It can be purchased off of the Chrysler website if you’re interested in reviewing it, or you can contact me at figure 2: p1486 — blockage check per the pcm at koer[email protected] and I will provide additional information on it.)figure 3: ldp pump mode sequence
Upon review of the manual, it shows that when the system is under test, it begins with a P1495 or P1496 check. This is a check to see if feed voltage applied (>10.4 volts) to the LDP has made its way back to the PCM to be grounded for pump operation. This is done at KOEO. figure 4: a forced evap monitor was run on our subject vehicle.
The second check is a P1494. This is done on startup and the LDP solenoid is energized to see if it’s able to operate on command. Note: Make sure that there is a good vacuum source to the pump so that false codes are not set. figure 5: p1495 and p1494 — check by the pcm at koeo and koer.
The third check, P1486, is a blockage test for the system. If the system passes this series of checks, the system has passed all electrical and mechanical testing for the system per the PCM.  figure 6: p1486 — blockage check per the pcm at koer and pump mode.
The series of waveforms in Figures 1 through 7 show the beginning portions of the test via a lab scope. figure 7: test mode shows less than 6 seconds —p0456 is set.The blue pattern is the LDP switch and the red pattern is the LDP solenoid. These serve as known-good patterns.

The next test in line is called “Pump Mode.” This is the time period for which the pump will be used to pressurize the system, and, per Chrysler, no codes will be set during this time period. Once the Pump Mode is complete, the system will then begin what is called “test mode” or “pump period.”
The EVAP system has now reached a point in its sequence where leaks can be tested. The size of the leak is based on when the purge solenoid stopped and how long the LDP switch remained in the open position. This time element was determined by Chrysler. Here are the time periods:
  — Less than 0.9 seconds equals a gross leak
  — Between 0.9 to 1.2 seconds equals a medium leak
  — Between 1.2 to 6 seconds equals a small leak

We now begin our story with a 2003 Dodge Caravan with a 3.3L engine. The EVAP system has set a code P0456 ­indicating that a small leak may be ­present. Note: It is always advisable to check for TSBs and any preliminary service information that may be available on the vehicle you are working on. This could save valuable diagnostic time.
A TSB check does indeed yield a bulletin: MIL Illumination, Erroneous DTC P0456 — EVAP Leak Monitor 0.020 Leak Detected. The fix per this bulletin is a new PCM. The PCM part number is not in the range indicated on this bulletin, so we will proceed with our diagnosis.
We start by forcing the monitor to run with a DRB III scan tool.
The activity is monitored with a lab scope to aid in the learning process. The following screens denote the process as witnessed:
A failure has now been confirmed; a code P0456 is stored in the controller’s memory.
A smoke test is done on the system and no smoke can be seen coming from the vehicle. We use a smoke machine with a flow meter to confirm the diagnosis. figure 8: this was a very ­difficult leak to find and isolate. the gas tank was dropped in an effort to ­isolate the leak.
The EVAP system is then isolated from the tank and retested, but the leak is not present.
Next, we test the fuel tank as a standalone unit. See Figures 8 and 9.
The leak has been found! Figure 9: The leak has been found!
A less-than-impressive repair to the gas tank was the cause of our leak. This Pulling Code case is now closed. 

The following two tabs change content below.

Carlton Banks

Technical Contributor for TechShop, Carlton is an emissions trainer for three Midwest states. He's made it a mission to find the truth in emissions-related codes.
Advertisement
Advertisement
Advertisement
Advertisement
Latest articles from our other sites:

Beck/Arnley Launches TRUE|Friction Brake Pad Series

Beck/Arnley has launched a new brake pad series that using the same type of material recommended by the vehicle’s manufacturer. TRUE|Friction pads are specifically designed to match the most current...More

TRW's Premium Chassis Program Tops 3,000 Mark

TRW’s North American (NA) Aftermarket Group has extended its all makes premium chassis program by an addition 527 SKUs. The total number of SKUs available from TRW now exceeds 3,000. Mark Thorpe,...More

Internal Engine Oil Consumption Diagnostics

Due to the variables in engine design and ­operating conditions, internal engine oil ­consumption complaints are often the most difficult to solve. In some cases, oil consumption might be more severe...More

Hyundai Fuel System, Emissions Diagnostics

Hyundai has done a good job of improving its ­offerings over the years from both an aesthetic and mechanical viewpoint. Complemented by a strong warranty and good value, the carmaker has been able to...More

Avoid The 'Warped Rotors' Trap, Find True Pulsation Cause

The expression “warped rotors” still seems prevalent in the brake service community. According to common lore, a warped rotor is the usual cause for pedal pulsation or vibration in the car or steering...More

Getting An Accurate Toyota Tire Pressure

Ambient temperature changes can dramatically alter tire pressure, which could cause a tire pressure monitoring system (TPMS) warning light to illuminate. The TPMS must be initialized based on the tire’s...More

Ernst Offers Socket Boss Universal Twist Lock Socket Tray

Versatility is a must for organizing any socket set. Capitalize on maximum configuration possibilities with the new Universal Twist-Lock Socket Tray from Ernst. Individual rails can be removed or switched...More

Ranger Introduces New Automatic Leverless Tire Changer

Ranger Products, a division of BendPak Inc., is bringing another new tire changer to market. Its latest R80DTXF tire changer features an automatic bead lifter, variable speed turntable and bilateral bead...More