Chevrolet Code P0135 is a diagnostic trouble code (DTC) that is associated with the engine control module (ECM). It is triggered when the ECM senses that the heater current of the heated oxygen sensor (HO2S) 1 is either greater than 3.125 amps or less than 0.25 amps for a period of 120 seconds. This code is often accompanied by other codes such as P0135, P0141, P0155, or P0161. In order to properly diagnose and fix this issue, the engine coolant temperature (ECT) must be greater than 50°C (122°F), the ignition voltage must be between 10-32 V, the engine run time must be greater than 300 s, and the engine speed must be between 500-3,000 RPM. There are several related service bulletins that specify solutions to the problem. Knowing the causes and solutions to this issue can help save valuable time and money.
Causes and Solutions of Chevrolet Code P0135
| Causes | Solutions |
|---|---|
| P0135 or P0155 | Replace the oxygen sensor |
| The ECM detects that the HO2S 1 heater current is greater than 3.125 amps, or less than 0.25 amps | Repair or replace damaged wiring and connectors |
| The DTCs set within 120 s during the heater current test when the above condition is met | Replace the ECM |
| Engine coolant temperature is greater than 50°C (122°F) | Check for a coolant leak |
P0135 or P0155
Oxygen sensors are used to monitor the amount of oxygen in the exhaust system. When the oxygen sensors become faulty, the engine control module (ECM) senses that the heater current of the heated oxygen sensor (HO2S) 1 is either greater than 3.125 amps or less than 0.25 amps for a period of 120 seconds. If this condition is met, the DTCs set and the code P0135 or P0155 will be triggered. To fix this issue, the oxygen sensor must be replaced.
Repair or Replace Damaged Wiring and Connectors
In some cases, the ECM may detect that the HO2S 1 heater current is greater than 3.125 amps or less than 0.25 amps for a period of 120 seconds, but the root cause of the issue may be due to damaged wiring or connectors. To solve this issue, the damaged wiring and connectors must be repaired or replaced.
Replace the ECM
If the DTCs set within 120 s during the heater current test, the ECM may be faulty and must be replaced.
Check for a Coolant Leak
If the engine coolant temperature is greater than 50°C (122°F), a coolant leak should be checked for. If a leak is detected, it must be repaired in order to fix the issue.
Conclusion
Chevrolet Code P0135 is a diagnostic trouble code (DTC) that can be triggered by a variety of causes. The most common causes are a faulty oxygen sensor, damaged wiring and connectors, and a faulty ECM. Solutions to the issue involve replacing the oxygen sensor, repairing or replacing damaged wiring and connectors, and replacing the ECM. Additionally, if the engine coolant temperature is greater than 50°C (122°F), a coolant leak should be checked for. Understanding the causes and solutions of Chevrolet Code P0135 can help save valuable time and money.
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