SPN 105 – Engine Intake Manifold #1 Temperature

Urgency and Driving Considerations

Fault code SPN 105 indicates a problem with the intake manifold temperature sensor circuit. The urgency depends on the specific failure mode indicator (FMI):

• FMI 3 (voltage high) and FMI 4 (voltage low): These are moderately urgent. The engine may run poorly due to using a default temperature value. Driving can continue but the fault should be diagnosed soon.

• FMI 2 (erratic/intermittent): Less urgent but should still be checked to prevent drivability issues. Intermittent faults can be tricky to diagnose.

• FMI 0 (data valid but above normal): Suggests a temperature issue that should be investigated promptly to prevent potential engine damage.

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In general, SPN 105 faults don't require immediately stopping but they should be diagnosed and repaired in a timely manner. If drivability is significantly impacted, stop driving and have the vehicle towed to avoid unsafe operation or additional damage.

Code Details

SPN 105 is a generic diagnostic trouble code that applies to all makes. The specific code format is:

• SPN: Suspect Parameter Number. 105 refers to the intake manifold temperature sensor.
• FMI: Failure Mode Indicator. Indicates the specific fault, such as a short circuit, open circuit, out of range value, etc.

Parts Involved

The main component is the intake manifold temperature sensor (sometimes called the intake air temperature sensor). This is a thermistor installed in the intake manifold that measures the temperature of the air entering the engine.

The sensor works with the engine control module (ECM), which supplies a reference voltage (often 5V) to the sensor. As temperature changes, the sensor's resistance changes, altering the signal voltage back to the ECM.

Common Causes

Potential causes of SPN 105 faults include:

• Damaged wiring or connectors causing open/short circuits
• Failing intake manifold temperature sensor
• Obstructed air flow through intake causing higher than expected temperatures

Diagnostic Steps

1. Scan for all fault codes. SPN 105 may appear with other codes that help pinpoint the issue.

2. Visually inspect the wiring and connectors between the ECM and sensor. Repair any obvious issues.

3. Check the sensor signal and reference voltages using a digital multimeter and compare to specifications.

4. If voltages are out of range, disconnect the sensor and recheck to determine if the issue is in the wiring or the sensor itself.

5. Inspect the intake air path for obstructions if temperature readings appear skewed high with a known good sensor.

Repair and Prevention

Repairs typically involve:

• Replacing or repairing damaged wiring
• Replacing the intake manifold temperature sensor
• Cleaning obstructed intake components

To prevent repeat failures:

• Keep electrical connections clean and secure
• Avoid impact damage to the sensor during other repairs
• Change the air filter regularly to prevent excess restriction

Repair Costs

Part costs vary but are typically around:

• Intake manifold temperature sensor: $30-100 USD / €25-85 EUR
• Pigtail connector (if required): $10-40 USD / €8-35 EUR

Labor time is typically 0.5-1 hour, so total cost with labor is often in the range of:

• $80-250 USD
• €70-210 EUR

Costs are higher if wiring repairs are extensive. Sensor replacement on some engines can require intake manifold removal, increasing labor time and cost.

Related Faults

Other codes that may appear with SPN 105 include:

• SPN 102 (intake manifold pressure sensor)
• SPN 106 (manifold absolute pressure sensor)
• SPN 110 (intake air temperature too high)

Resolving the root cause of SPN 105 often clears related fault codes as well.

Frequently Asked Questions about SPN 105 Fault Codes

What does SPN 105 indicate?

SPN 105 is a generic diagnostic trouble code that refers to a problem with the intake manifold temperature sensor circuit. The specific issue is determined by the failure mode indicator (FMI) included with the code.

What are the different FMIs associated with SPN 105?

Common FMIs for SPN 105 include:

• FMI 0: Data valid but above normal
• FMI 1: Data valid but below normal
• FMI 2: Data erratic, intermittent, or incorrect
• FMI 3: Voltage above normal or shorted high
• FMI 4: Voltage below normal or shorted low
• FMI 17/18: Circuit voltage above/below normal

How urgent is an SPN 105 fault?

The urgency depends on the FMI:

• FMI 3/4 are moderately urgent. The engine may run poorly but driving can continue with diagnosis scheduled soon.
• FMI 2 is less urgent but should be checked to prevent drivability issues.
• FMI 0 suggests a temperature issue that should be investigated promptly to avoid engine damage.

In general, SPN 105 doesn't require immediately stopping but should be diagnosed and repaired in a timely manner. Stop driving if drivability is significantly impacted.

What component does SPN 105 refer to?

SPN 105 refers to the intake manifold temperature sensor, sometimes called the intake air temperature sensor. This thermistor is installed in the intake manifold to measure the temperature of air entering the engine.

How does the intake manifold temperature sensor work?

The sensor works with the engine control module (ECM). The ECM supplies a reference voltage (often 5V) to the sensor. As temperature changes, the sensor's resistance changes, altering the signal voltage sent back to the ECM.

Where is the intake manifold temperature sensor located?

The sensor is typically threaded into the intake manifold near the front of the engine, often close to the turbocharger if equipped. Consult vehicle-specific service information for exact location.

What are common causes of SPN 105 faults?

Potential causes include:

• Damaged wiring or connectors causing open or short circuits
• Failing intake manifold temperature sensor
• Obstructed air flow through the intake causing higher than expected temperatures

How is SPN 105 diagnosed?

Key diagnostic steps:

1. Scan for all fault codes. SPN 105 may appear with other codes that help pinpoint the issue.
2. Visually inspect wiring and connectors between the ECM and sensor. Repair obvious issues.
3. Check sensor signal and reference voltages with a multimeter and compare to specifications.
4. If voltages are out of range, disconnect the sensor and recheck to isolate the problem to the wiring or sensor.
5. Inspect the intake air path for obstructions if temperature readings are skewed high with a known good sensor.

What repairs are needed for SPN 105?

Repairs typically involve:

• Replacing or repairing damaged wiring
• Replacing the intake manifold temperature sensor
• Cleaning obstructed intake components

How much does it cost to fix SPN 105?

Repair costs vary but are often in the range of:

• $80-250 USD
• €70-210 EUR

This includes $30-100 USD / €25-85 EUR for the sensor, $10-40 USD / €8-35 EUR for the wiring connector if needed, and 0.5-1 hour of labor. Costs increase if wiring repairs are extensive or intake manifold removal is required for sensor access on some engines.

Can I drive with an SPN 105 fault?

It depends on the FMI and severity. Driving can generally continue with SPN 105 faults, especially intermittent ones, but diagnosis and repair should be scheduled promptly. If drivability is significantly impacted, stop driving to prevent damage and have the vehicle towed.

Will SPN 105 cause the engine to shut down?

Not typically. The ECM will use a default temperature value if it detects an issue with the intake manifold temperature sensor circuit. This may cause the engine to run poorly but complete shutdown is unlikely from SPN 105 alone.

Can SPN 105 cause other issues?

Yes, an intake manifold temperature sensor fault can cause:

• Rough running
• Lack of power
• Increased emissions
• Reduced fuel economy
• Improper transmission shifting on some vehicles

What other components can cause SPN 105?

While the sensor itself is the most common cause, other potential sources of SPN 105 include:

• Damaged or corroded wiring and connectors
• Faulty ECM (rare)
• Obstructed intake air flow
• Low coolant level (sensor measures air temperature but can be affected by coolant temperature)

How can I prevent SPN 105?

Prevention measures include:

• Keeping electrical connections clean and secure
• Avoiding impact damage to the sensor during other repairs
• Changing the air filter regularly to prevent excess restriction
• Maintaining proper coolant level

What other codes may appear with SPN 105?

Related codes can include:

• SPN 102 (intake manifold pressure sensor)
• SPN 106 (manifold absolute pressure sensor)
• SPN 110 (intake air temperature too high)

Resolving the root cause of SPN 105 often clears these related codes as well.

Is SPN 105 a generic code?

Yes, SPN 105 is a generic code that applies to all makes and models of vehicles equipped with an electronic engine control system and intake manifold temperature sensor. The specific code format and diagnostic details may vary by manufacturer.

What tools are needed to diagnose SPN 105?

Basic diagnosis of SPN 105 requires:

• An OBD-II scanner to read fault codes
• A digital multimeter to measure circuit voltages
• A wiring diagram for the specific vehicle

More advanced diagnosis may require:

• An oscilloscope to check for intermittent faults
• Manufacturer-specific diagnostic software for more detailed data and testing

What are the FMI 3 and FMI 4 voltage ranges for SPN 105?

• FMI 3 (voltage high) is typically set when signal voltage exceeds 4.8V.
• FMI 4 (voltage low) is typically set when signal voltage drops below 0.2V.

The exact voltage thresholds vary by manufacturer and should be confirmed in service information for the specific vehicle being diagnosed.

How do I know if the intake manifold temperature sensor is faulty?

Key signs of a faulty intake manifold temperature sensor include:

• SPN 105 fault codes
• Measured signal voltages outside the expected range
• Erratic or implausible temperature readings
• Failure to change resistance/voltage as temperature changes

Confirming a faulty sensor usually involves measuring its resistance at various temperatures and comparing to specifications. A sensor that measures out of range or fails to change resistance with temperature change is faulty.