Circuit Description
The powertrain control module (PCM) uses information from the intake air temperature (IAT) and the engine coolant temperature (ECT) sensors to determine ambient temperature at cold startup. Alcohol content (percentage) information is supplied to the PCM from the fuel composition sensor. This information is used by the technician in diagnosing symptom related complaints such as hard starting in cold ambient temperatures. The PCM monitors the fuel frequency during the first 30 seconds of run time. When the PCM detects alcohol content that is too high for a given ambient temperature, this DTC sets.
Conditions for Running the DTC
The ECT and IAT have less than 4.5°C (8°F) difference at cold start up.
Conditions for Setting the DTC
If the fuel composition is above the given threshold for the ambient temperature, for 25 seconds of the 30 second interval.
Action Taken When the DTC Sets
| • | The control module stores the DTC in history after the first failure but will not illuminate the malfunction indicator lamp (MIL). |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame and Failure Records. |
Conditions for Clearing the MIL/DTC
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. |
| • | A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle. |
| • | Use the scan tool Clear Information function. |
Diagnostic Aids
| • | The system is designed for use of regular unleaded fuel to any ethanol concentration up to 85 percent (E85). |
| • | When the ambient temperature drops below -10°C (+14°F), a winter blend of 70 percent (E70), or less is recommended for cold weather starting. |
| • | The use of methanol fuels may set this DTC. |
| • | Use of methanol fuel or high concentration of ethanol may cause DTCs P0169 and P0179 to set. |
| • | Other contamination such as water and salts may cause this DTC to set. |
The table below shows the maximum thresholds of a given ethanol content (percentage) versus the ambient temperature at which a DTC P0169 will set.
Temperature | Ethanol Content | Frequency Hz |
|---|---|---|
-40°C (-40°F) and colder | 55% | 105 Hz |
From -30 to -10°C (-22 to + 14°F) | 76% | 126 Hz |
-5°C (+23°F) | 81% | 131 Hz |
0°C (32°F) and warmer | 88% | 138 Hz |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Engine controls. | -- | Go to Step 2 | |
2 | Was DTC P0179 also set? | -- | Go to DTC P0179 | Go to Step 3 |
Read the fuel composition frequency on the scan tool. Is the frequency above the specified value? | 139 Hz | Go to Step 4 | Go to Step 5 | |
4 |
Is the fuel composition frequency below the specified value? | 138 Hz | Go to Step 6 | Go to Diagnostic Aids |
5 |
Is the fuel composition frequency below the specified value? | 138 Hz | Go to Step 6 | Go to Diagnostic Aids |
6 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 7 |
7 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK |
