P1402 – Exhaust Flap Control Circuit Low (some manufacturers)

Overview

The P1402 diagnostic trouble code indicates a malfunction in the Exhaust Gas Recirculation (EGR) system. This code is generally defined as "EGR metering orifice restricted", though the exact definition may vary slightly between vehicle manufacturers.

If this code is present, it's best to have the vehicle inspected by a qualified mechanic as soon as possible, as driving with a malfunctioning EGR system can lead to increased emissions, reduced fuel economy, and potential engine damage. However, if the vehicle is running normally otherwise, it is generally safe to drive it short distances to a repair shop.

EGR System Components

The EGR system recirculates a portion of the exhaust gases back into the engine intake to lower combustion temperatures and reduce NOx emissions. The main components of the EGR system include:

• EGR Valve: Controls the flow of exhaust gases into the intake manifold
• EGR Temperature Sensor: Monitors the temperature of the gases flowing through the EGR system
• Differential Pressure Feedback EGR (DPFE) Sensor: Measures the pressure difference across the EGR valve to determine flow
• EGR Vacuum Solenoid/Modulator: Controls the vacuum signal to the EGR valve
• EGR Passages/Tubes: Carry the exhaust gases from the exhaust manifold to the intake manifold

Common Causes

Some of the most common causes of a P1402 code include:

• Clogged or stuck EGR valve or passages due to carbon buildup
• Faulty EGR temperature sensor
• Faulty DPFE sensor
• Damaged or leaking EGR vacuum lines
• Malfunctioning EGR vacuum solenoid/modulator
• Damaged or corroded electrical wiring/connectors in the EGR system

Diagnosis

To properly diagnose the root cause of a P1402 code, follow these steps:

1. Visually inspect all accessible EGR system components, wiring, and vacuum lines for damage, cracks, or loose connections.
2. Test the EGR valve for proper operation using a vacuum pump. The valve should open and close smoothly.
3. Check the resistance of the EGR temperature sensor using a multimeter. At room temperature (21°C/70°F), resistance should be around 2.4-3.2 kΩ.
4. With the engine running, use a vacuum gauge to check for proper vacuum signals at the EGR valve and DPFE sensor. Readings should vary with engine speed.
5. Use a multimeter to check for proper voltage signals at the DPFE sensor. With the key on, engine off, voltage should be around 4.8-5.2 V.

Repair Solutions

Depending on the diagnosed root cause, common repairs for a P1402 code may include:

• Cleaning the EGR valve and passages to remove carbon buildup
• Replacing a faulty EGR temperature sensor, DPFE sensor, or vacuum solenoid
• Replacing damaged EGR vacuum lines or electrical wiring
• Replacing a defective EGR valve that cannot be cleaned

For detailed, step-by-step repair instructions, consult a vehicle-specific repair manual or online repair database.

Repair Costs

The cost to repair an EGR system will depend on the specific component(s) that need replacement. Typical costs for common parts include:

• EGR Valve: $150-$500 (£110-£370 / €130-€440)
• EGR Temperature Sensor: $30-$100 (£20-£75 / €25-€90)
• DPFE Sensor: $50-$200 (£35-£150 / €45-€180)
• EGR Vacuum Solenoid: $40-$150 (£30-£110 / €35-€130)

Labor costs will vary depending on the repair shop and the vehicle, but can range from $50-$150 (£35-£110 / €45-€130) per hour, with most repairs taking 1-3 hours.

Prevention

To help prevent EGR system issues and P1402 codes, consider the following:

• Have the EGR system cleaned regularly to remove carbon buildup, especially on higher mileage vehicles
• Promptly repair any vacuum leaks or other engine issues that can affect EGR operation
• Address any other engine fault codes that may be related to or causing EGR problems

Associated Issues

Other symptoms that may be present along with a P1402 code include:

• Rough idle or stalling
• Hesitation or stumbling on acceleration
• Increased fuel consumption
• Illuminated Check Engine Light

Other fault codes that may be set along with P1402 include:

• P0401 – Insufficient EGR flow
• P0406 – EGR system performance

If these or other codes are present, they should be diagnosed and repaired as well to ensure proper engine operation.

Frequently Asked Questions About P1402

What does OBD-II code P1402 mean?

Code P1402 stands for "EGR Metering Orifice Restricted". This indicates a problem with the Exhaust Gas Recirculation (EGR) system, specifically that the metering orifice which controls EGR flow is clogged or restricted.

Is it safe to drive with a P1402 code?

It depends on the severity. A P1402 code itself does not pose an immediate safety risk, but driving with a malfunctioning EGR system can lead to increased emissions, reduced fuel economy, and potential engine damage over time. It's best to have the issue diagnosed and repaired as soon as possible.

What are the common symptoms of a P1402 code?

• Illuminated Check Engine Light
• Rough idle or stalling
• Hesitation or stumbling on acceleration
• Increased fuel consumption
• Failed emissions test

What are the common causes of a P1402 code?

• Clogged EGR valve or passages due to carbon buildup
• Faulty EGR temperature sensor
• Faulty Differential Pressure Feedback EGR (DPFE) sensor
• Damaged or leaking EGR vacuum lines
• Malfunctioning EGR vacuum solenoid/modulator
• Damaged or corroded electrical wiring/connectors in the EGR system

How is a P1402 code diagnosed?

1. Visually inspect all accessible EGR system components, wiring, and vacuum lines for damage or loose connections.
2. Test the EGR valve for proper operation using a vacuum pump.
3. Check the resistance of the EGR temperature sensor with a multimeter.
4. Use a vacuum gauge to check for proper vacuum signals at the EGR valve and DPFE sensor.
5. Use a multimeter to check for proper voltage signals at the DPFE sensor.

What tools are needed to diagnose a P1402 code?

The main tools needed are a code reader/scan tool to retrieve the code, a multimeter for electrical tests, and a vacuum gauge for testing vacuum signals. A hand vacuum pump is also helpful for testing the EGR valve operation.

How much does it cost to repair a P1402 code?

The cost depends on the root cause. An EGR valve replacement typically costs $150-$500, while a temperature sensor or DPFE sensor replacement is usually $30-$200. Total repair costs with labor are often in the $200-$600 range.

Can I clean a clogged EGR valve myself?

In many cases, yes. Carefully remove the EGR valve and clean the carbon buildup from the valve and passages with carburetor cleaner and a wire brush. However, if the valve is heavily corroded or damaged, replacement is necessary.

How often should the EGR system be cleaned to prevent issues?

For preventive maintenance, it's a good idea to clean the EGR valve and passages every 50,000-80,000 miles, especially on higher mileage vehicles. Vehicles driven mainly on short trips are more prone to EGR clogging.

Can a P1402 code cause a vehicle to fail an emissions test?

Yes, a malfunctioning EGR system can cause a vehicle to fail an emissions test due to higher than acceptable NOx levels in the exhaust. The EGR system must be repaired in order to pass a retest.

Will a P1402 code trigger a "Check Engine" light?

Yes, a P1402 code will illuminate the "Check Engine" or "Service Engine Soon" light on the vehicle's dashboard. The light may be steady or flashing depending on the severity of the issue.

Can a malfunctioning EGR system damage the engine?

Potentially, yes. A stuck-open EGR valve can allow excessive exhaust gases into the intake, leading to rough running, misfires, and possible combustion chamber damage over time. A stuck-closed valve may cause pre-ignition or detonation due to higher combustion temperatures.

What other codes may be present along with P1402?

Related codes that may appear alongside P1402 include:

• P0400 – Exhaust Gas Recirculation Flow Malfunction
• P0401 – Exhaust Gas Recirculation Flow Insufficient Detected
• P0402 – Exhaust Gas Recirculation Flow Excessive Detected
• P0403 – Exhaust Gas Recirculation Circuit Malfunction
• P0404 – Exhaust Gas Recirculation Circuit Range/Performance
• P0405 – Exhaust Gas Recirculation Sensor A Circuit Low
• P0406 – Exhaust Gas Recirculation Sensor A Circuit High

Can a P1402 code be caused by issues other than the EGR system?

While less common, a P1402 code may be triggered by issues such as a vacuum leak, a malfunctioning Powertrain Control Module (PCM), or a wiring problem that mimics an EGR fault. Thorough diagnosis is key to isolating the actual root cause.

How does the EGR system affect vehicle emissions?

The EGR system reduces the formation of nitrogen oxides (NOx) in the engine's exhaust by recirculating a portion of the exhaust gases back into the combustion chambers. This lowers peak combustion temperatures, which inhibits NOx formation. A malfunctioning EGR system can cause increased NOx emissions.

Can a software update fix a P1402 code?

In rare cases, a software reflash or update to the vehicle's PCM may resolve a P1402 code if it is being triggered erroneously due to a programming issue. However, a software update will not fix a physically clogged or malfunctioning EGR valve or other hardware issues.

Is the EGR system covered under a vehicle's emissions warranty?

In most cases, yes. The EGR valve and related components are usually covered under the emissions warranty for 8 years or 80,000 miles, whichever comes first. However, exact coverage may vary by vehicle make and model.

Can a P1402 code keep coming back after repairs?

Yes, if the root cause was not properly diagnosed and fixed, or if there are multiple underlying issues, a P1402 code may reappear even after parts are replaced. Thorough diagnosis and repair are essential for a long-term fix.

What are the differences between the EGR systems on gasoline and diesel engines?

While the basic purpose is the same, EGR systems on gasoline and diesel engines differ in their specific designs and components. Diesel EGR valves often have an integrated cooling system to lower the temperature of the recirculated exhaust gases. Diesel EGR systems also tend to have higher recirculation flow rates.

Can an aftermarket performance tuner or chip cause a P1402 code?

Yes, an aftermarket tuner or performance chip that modifies the EGR system parameters or disables it entirely may trigger a P1402 code. It's best to use only tuners that are emissions-compliant and do not alter the factory EGR calibration.