The Cen-Tech Can OBDII 94169 scanner can help diagnose various car problems, including the P0128 code, which indicates an issue with the coolant thermostat. This code often points to a malfunctioning coolant temperature sensor. This guide outlines diagnostic tests based on a service manual for a specific vehicle, offering potential solutions for a P0128 error. While not a direct replacement for a Cen-tech Can Obdii 94169 Manual, this information provides valuable troubleshooting insights. A subscription to ALLDATAdiy.com can offer comprehensive service manuals for your specific vehicle make and model.
Testing the Coolant Temperature Sensor (B11/4) for P0128
The following tests focus on the Coolant Temperature Sensor (B11/4), a common culprit for the P0128 code.
Test 1: Checking the Actual Value of B11/4
Purpose: This test verifies if the sensor accurately reads the coolant temperature.
Procedure:
- Run the engine.
- Using a suitable diagnostic tool (like the Cen-Tech 94169), access the live data stream and locate the “Coolant Temperature” parameter.
- Observe the actual value displayed. It should change accordingly as the engine warms up.
Expected Result: The actual value should fluctuate realistically with the engine temperature. If the value remains static or out of range, proceed to the next test.
Test 2: Testing Signal Voltage of B11/4
Purpose: This test measures the voltage signal from the sensor to determine its functionality.
Procedure:
- Switch off the ignition.
- Connect the appropriate diagnostic socket box (36 and 126-pin) to the ME-SFI control module (N3/10).
- Connect adapter cable no. 220 589 00 99 32 to the coolant temperature sensor (B11/4).
- Consult the following table for specified voltage values at various temperatures:
| Temperature (°C) | Voltage (V) |
|---|---|
| 20 | 3.36…3.48 |
| 30 | 2.91…2.97 |
| 40 | 2.40…2.45 |
| 50 | 1.94…1.98 |
| 60 | 1.53…1.57 |
| 70 | 1.18…1.21 |
| 80 | 0.92…0.93 |
| 90 | 0.70…0.73 |
| 100 | 0.54…0.56 |
| 110 | 0.42…0.44 |
Expected Result: Measured voltage should fall within the specified range for the corresponding temperature. If not, a faulty sensor or wiring issue is likely.
Test 3: Testing Internal Resistance of B11/4
Purpose: This test measures the sensor’s internal resistance to assess its condition.
Procedure:
- Switch off the ignition.
- Disconnect the connector at the coolant temperature sensor (B11/4).
- Connect adapter cable no. 220 589 00 99 32 to the coolant temperature sensor (B11/4).
- Refer to the following table for specified resistance values at different temperatures:
| Temperature (°C) | Resistance (Ohms) |
|---|---|
| 20 | 2940…3240 |
| 30 | 1900…2100 |
| 40 | 1265…1395 |
| 50 | 855…945 |
| 60 | 590…650 |
| 70 | 420…460 |
| 80 | 305…335 |
| 90 | 220…240 |
| 100 | 160…180 |
| 110 | 115…145 |
Expected Result: The measured resistance should correlate with the specified range for the given temperature. If not, the sensor likely needs replacement.
Conclusion
These tests offer a starting point for diagnosing a P0128 error code, potentially related to a faulty coolant temperature sensor. While a dedicated cen-tech can obdii 94169 manual might provide more specific instructions, this information, coupled with a quality OBDII scanner like the Cen-Tech 94169, can aid in troubleshooting. If problems persist, consult a qualified mechanic or refer to a comprehensive service manual for your specific vehicle.
