When a Chevrolet vehicle is experiencing issues with its engine, it can be difficult to pinpoint the cause without a proper diagnosis. One of the most common issues is the P2078 code, which stands for Intake Manifold Tuning (IMT) Valve Position Sensor Circuit High Voltage. This code occurs when the engine is running for more than one second, the intake air temperature is above 15°C, and the Manifold Absolute Pressure (MAP) is below 30 kPa for six seconds. So what causes this code? There are a few potential causes, including a shorted 5-volt reference circuit, or a scan tool 5-volt reference parameter reading that is outside of the 4.8-5.2 volts range. To help troubleshoot this issue, PIP5094 is a related Service Bulletin that can provide more guidance. Below is a table outlining the causes and potential solutions for the P2078 code.
Potential Causes and Solutions for P2078
| Causes | Solutions |
| —— | ——— |
| Shorted 5-volt reference circuit | Check the scan tool 5-volt reference parameter readings |
| Scan tool 5-volt reading outside 4.8-5.2 volts range | Check the 5-volt reference circuit |
Shorted 5-Volt Reference Circuit
When the 5-volt reference circuit is shorted, it can cause the P2078 code to be triggered. This can be difficult to diagnose without a proper scan tool to measure the voltage. If the voltage is higher than 4.8 volts, it can indicate that the 5-volt reference circuit is shorted. If this is the case, the circuit should be checked for any signs of damage or corrosion.
Scan Tool 5-Volt Reading Outside 4.8-5.2 Volts Range
If the scan tool 5-volt reference parameter reading is outside of the 4.8-5.2 volts range, it can also cause the P2078 code to be triggered. The easiest way to diagnose this issue is to use a scan tool to measure the voltage. If the voltage is outside of the range, it can indicate that the 5-volt reference circuit is not functioning properly.
PIP5094 Service Bulletin
The PIP5094 service bulletin is a great resource for troubleshooting the P2078 code. It outlines the causes and potential solutions for the code, as well as providing detailed information on how to diagnose and repair the issue.
Conclusion
The P2078 code is a common issue for Chevrolet vehicles that can be difficult to diagnose without the right tools. By understanding the potential causes and solutions for the code, it can help to narrow down the issue and get the vehicle back on the road. Professional diagnosis and repair may be necessary to resolve the issue and clear the Chevrolet Code P2078.
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