Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSVOLVO1997850 L5-2.4L VIN 55 B5254SREPAIR AND DIAGNOSISA L L DIAGNOSTIC TROUBLE CODES ( DTC )TESTING AND INSPECTIONDIAGNOSTIC TROUBLE CODE DESCRIPTIONSMANUFACTURER CODE CHARTSENGINE CONTROL SYSTEMDETAILED DTC DESCRIPTIONSDTC EFI-153 REAR HEATED OXYGEN SENSOR SIGNAL
1997 Volvo 850 L5-2.4L VIN 55 B5254S
DTC EFI-153 Rear Heated Oxygen Sensor Signal
1997 Volvo 850 L5-2.4L VIN 55 B5254SSECTION DTC EFI-153 Rear Heated Oxygen Sensor Signal
1-5-3 REAR HEATED OXYGEN SENSOR SIGNAL
Trouble Code Conditions
- The rear heated oxygen sensor (HO2S) must be at operating temperature and have the correct output voltage to affect fuel trim and monitor the three-way catalytic converter (TWC) and front heated oxygen sensor. Monitoring of the heated oxygen sensor function starts approx. 3 minutes after heated oxygen sensor heating starts. Diagnostic trouble code (DTC) EFI-153 is stored if there is a fault in the front or rear heated oxygen sensors or their cabling that affects the output voltage from the rear heated oxygen sensor.
Substitute value(s)
- Twin heated oxygen sensor fuel trim is disabled.
- Three-way catalytic converter diagnostic disabled.
Possible source(s)
Signal too high:
- Short-circuit to supply voltage in front heated oxygen sensor signal cable (+).
- Short-circuit to supply voltage in front heated oxygen sensor signal cable (-).
- Short-circuit to supply voltage in rear heated oxygen sensor signal cable (+).
- Short-circuit to supply voltage in rear heated oxygen sensor signal cable (-).
- Defective front heated oxygen sensor.
- Defective rear heated oxygen sensor.
Signal too low:
- Short-circuit to ground in front heated oxygen sensor signal cable (+).
- Short-circuit to ground in front heated oxygen sensor signal cable (-).
- Short-circuit to ground in rear heated oxygen sensor signal cable (+).
- Short-circuit to ground in rear heated oxygen sensor signal cable (-).
- Defective front heated oxygen sensor.
- Defective rear heated oxygen sensor.
Signal missing:
- Open-circuit in signal cable.
- Open-circuit in signal cable.
- Defective rear heated oxygen sensor.
Faulty signal:
- Signal cable (+) short-circuited to signal cable.
- defective rear heated oxygen sensor.
Fault symptom(s)
- None.
Trouble Code Conditions
- The rear heated oxygen sensor (HO2S) must be at operating temperature and have the correct output voltage to affect fuel trim and monitor the three-way catalytic converter (TWC) and front heated oxygen sensor. Monitoring of the heated oxygen sensor function starts approx. 3 minutes after heated oxygen sensor heating starts. Diagnostic trouble code (DTC) EFI-153 is stored if there is a fault in the front or rear heated oxygen sensors or their cabling that affects the output voltage from the rear heated oxygen sensor.
Substitute value(s)
- Twin heated oxygen sensor fuel trim is disabled.
- Three-way catalytic converter diagnostic disabled.
Possible source(s)
Signal too high:
- Short-circuit to supply voltage in front heated oxygen sensor signal cable (+).
- Short-circuit to supply voltage in front heated oxygen sensor signal cable (-).
- Short-circuit to supply voltage in rear heated oxygen sensor signal cable (+).
- Short-circuit to supply voltage in rear heated oxygen sensor signal cable (-).
- Defective front heated oxygen sensor.
- Defective rear heated oxygen sensor.
Signal too low:
- Short-circuit to ground in front heated oxygen sensor signal cable (+).
- Short-circuit to ground in front heated oxygen sensor signal cable (-).
- Short-circuit to ground in rear heated oxygen sensor signal cable (+).
- Short-circuit to ground in rear heated oxygen sensor signal cable (-).
- Defective front heated oxygen sensor.
- Defective rear heated oxygen sensor.
Signal missing:
- Open-circuit in signal cable.
- Open-circuit in signal cable.
- Defective rear heated oxygen sensor.
Faulty signal:
- Signal cable (+) short-circuited to signal cable.
- defective rear heated oxygen sensor.
Fault symptom(s)
- None.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.