Easy one-page printout for the garage or repair shop
This summary uses the existing diagnostic information shown in full below.
This code means that the car's computer thinks the sensor that checks for ammonia in the exhaust is getting too high of a signal. It's like if your TV remote was sending too strong a signal to the TV.
The P24E4 code indicates that the signal from the NH3 (ammonia) sensor is higher than expected, suggesting a potential issue with the sensor or its circuit.
The NH3 sensor is part of the vehicle's emissions control system, specifically monitoring ammonia levels in the exhaust to help reduce harmful emissions. A 'circuit high' condition suggests that the sensor is outputting a voltage higher than the specified range, which could be due to a sensor fault, wiring issue, or a problem with the control module.
• Check Engine Light is on
• Possible decrease in fuel efficiency
• Failed emissions test
• Faulty NH3 sensor
• Wiring issues such as shorts or opens in the sensor circuit
• Faulty powertrain control module (PCM)
NH3: Ammonia, a compound of nitrogen and hydrogen
PCM: Powertrain Control Module, the vehicle's main computer
• Use an OBD-II scanner to confirm the code
• Visually inspect the NH3 sensor and wiring for damage
• Test the sensor's voltage output with a multimeter
• Replace the NH3 sensor if faulty
• Repair or replace damaged wiring or connectors
• Replace the PCM if necessary
• OBD-II scanner
• Multimeter
• Basic hand tools
$150 - $500
Moderate
• Toyota Prius
• Ford F-150
• Chevrolet Silverado
• Regular maintenance checks
• Ensure proper installation of sensors
• Avoid exposure to extreme conditions
Sensor Issue
• Have the vehicle inspected by a professional
• Do not ignore the Check Engine Light
• Consider regular emissions testing
Check with the manufacturer for emissions-related warranty coverage.
This code has become more common with the increased use of advanced emissions systems in modern vehicles.
Moderate – While not immediately dangerous, it can affect emissions and fuel efficiency.
Driving with this code may lead to increased emissions, which could be illegal in some areas.
• Engine at operating temperature
• Vehicle in closed-loop mode
The NH3 sensor is typically located in the exhaust system, downstream of the catalytic converter.
Q: Can I drive with a P24E4 code?
A: While the car may still run, it's best to address the issue to avoid increased emissions and potential damage.
Q: How do I reset the Check Engine Light?
A: After repairs, the light can be reset using an OBD-II scanner, or it may turn off after several drive cycles if the issue is resolved.
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Universal · Digital multimeter
A solid entry-level multimeter for voltage, continuity, resistance, and basic electrical troubleshooting.
Helpful for checking voltage drops, grounds, and basic circuit health when modules are not communicating.
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Universal · Wire connectors and repair kit
Useful when diagnosis points toward damaged wiring, corroded terminals, or connector repairs.
Useful if diagnosis points toward damaged connectors, wiring, or terminal repairs.
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Fitment Required · Vehicle-fitment part
Relevant when catalyst-efficiency or emissions faults persist after proper diagnosis.
Catalyst-efficiency faults sometimes point toward converter problems after proper testing.
Catalytic converters are highly vehicle-specific and should not be purchased by code alone.
View options on AmazonThese parts may be related to this fault category, but a code by itself does not confirm exact fitment or guarantee that replacing a part will solve the problem.