DTC 1-5-3
1-5-3 REAR HEATED OXYGEN SENSOR SIGNALPreconditions for DTC
^ In order for the Rear Heated Oxygen Sensor (HO2S) to be able to affect the fuel trim and monitor the Three-Way Converter (TWC) and front HO2S, it must be at operating temperature and at the correct output voltage. Monitoring of the HO2S function begins approx. 3 minutes after the HO2S preheating phase begins. If there is a fault with the front or rear HO2S or their leads, so that the output voltage from the rear HO2S differs from the permitted value, DTC 1-5-3 is set.
Substitute value
^ Fuel trim is inhibited.
^ TWC diagnosis is inhibited.
Fault sources
^ Signal too high:
- Signal lead (+) short circuited to voltage supply.
- Signal lead (-) short circuited to voltage supply.
- Defective front HO2S.
- Defective rear HO2S.
^ Signal too low:
- Signal lead (+) short circuited to ground.
- Signal lead (-) short circuited to ground.
- Break in signal lead (+).
- Break in signal lead (-).
- Defective front HO2S.
- Defective rear HO2S.
^ Faulty signal:
- Signal lead (+) short circuited to signal lead (-).
- Defective rear HO2S.
Fault symptom
^ None.
TESTING PROCEDURE
Other DTCs
^ Read the other DTCs.
If DTC 5-2-2 is stored:
- See: Testing By Trouble Code, DTC 5-2-2 Rear HO2S, Preheating.
If DTC 2-1-2 is stored:
- See: Testing By Trouble Code, DTC 2-1-2 Front HO2S, Signal.
If DTC 5-2-2 or 2-1-2 is not stored:
- Check Status message.
Status Message
^ Check current status message.
If Status message is: Permanent fault, signal too high:
- See: Testing By Trouble Code, DTC 2-1-2 Front HO2S, Signal.
If Status message is: Permanent fault, signal too low:
- Proceed to: PERMANENT FAULT, SIGNAL TOO LOW section below.
If Status message is: Permanent fault, faulty signal:
- Proceed to: PERMANENT FAULT, FAULTY SIGNAL section below.
If Status message is: Intermittent fault, signal too high:
- See: Testing By Trouble Code, DTC 2-1-2 Front HO2S, Signal.
If Status message is: Intermittent fault, signal too low:
- Proceed to: INTERMITTENT FAULT, SIGNAL TOO LOW section below.
If Status message is: Intermittent fault, faulty signal:
- Proceed to: INTERMITTENT FAULT, FAULTY SIGNAL section below.
PERMANENT FAULT, SIGNAL TOO LOW
Checking the Signal Lead (+), Rear HO2S
^ Switch Ignition OFF.
^ Wait for approx. 150 seconds.
^ Disconnect the rear HO2S (grey connector).
^ Connect an ohmmeter between the HO2S connector 4 (to ECM) and ground.
The ohmmeter should show approx. 100K ohms.
If reading is OK:
- Check the signal lead (-), rear HO2S.
If ohmmeter shows infinite resistance:
- Check the ECM's connector.
If the ohmmeter shows approx. 0 ohms:
- Check lead between rear HO2S connector 4 and ECM A34 for signs of short circuiting to ground.
Checking the ECM's Connector
^ Switch Ignition OFF.
^ Rear HO2S disconnected.
^ Rectify the ECM connector with regard to contact resistance and oxidation.
^ ECM connected.
^ Connect an ohmmeter between HO2S connector 4 (to ECM) and ground.
The ohmmeter should show approx. 100K ohms.
If reading is OK:
- Source of DTC is poor contact in the ECM's connector.
If reading is incorrect:
- Check lead between rear HO2S connector 4 and ECM A34 for signs of a break.
Checking the Signal Lead (-), Rear HO2S
^ Switch Ignition OFF.
^ Rear HO2S disconnected.
^ Connect an ohmmeter between the HO2S connector 3 (to ECM) and ground.
The ohmmeter should show approx. 200 ohms.
If reading is OK:
- Check the signal, rear HO2S.
If ohmmeter shows infinite resistance:
- Check the ECM's connector.
If the ohmmeter shows approx. 0 ohms:
- Check the front HO2S.
Checking the ECM's Connector
^ Switch Ignition OFF.
^ Rear HO2S disconnected.
^ Rectify the ECM connector with regard to contact resistance and oxidation.
^ ECM connected.
^ Connect an ohmmeter between HO2S connector 3 (to ECM) and ground.
The ohmmeter should show approx. 200 ohms.
If reading is OK:
- Source of DTC is poor contact in ECM's connector.
If reading is incorrect:
- Check lead between rear HO2S connector 3 and ECM A19 for signs of a break.
Checking the Front HO2S
^ Switch Ignition OFF.
^ Rear HO2S disconnected.
^ Disconnect the front HO2S (black connector).
^ Connect an ohmmeter between rear HO2S connector 3 (to ECM) and ground.
The ohmmeter should show approx. 200 ohms.
If reading is OK:
- Test with a new front HO2S.
If reading is incorrect:
- Check the lead between front HO2S connector 3 and ECM A33 and the lead between the rear HO2S connector 3 and ECM A19 for signs of short circuiting to ground.
Checking the Signal, Rear HO2S
^ Switch Ignition OFF.
^ Connect the rear HO2S.
^ START the engine and let it run at idling speed.
^ Look up the DTC parameter.
^ Read the value on the rear HO2S.
The signal should have left its bottom setting (-0.165 Volts) and stabilized between 0.1 - 0.9 Volts within approx. 10 minutes.
If reading is OK:
- The source of the DTC is poor contact in rear HO2S connector. Check that the connector tabs are not damaged.
If reading is incorrect:
- Test with a new rear HO2S.
NOTE: Rust-removal spray or grease may not be used in the HO2S connector.
PERMANENT FAULT, FAULTY SIGNAL
Checking the Rear HO2S
^ Switch Ignition OFF.
^ Wait for approx. 150 seconds.
^ Disconnect the rear HO2S (grey connector).
^ Connect an ohmmeter between the HO2S connector 3 and 4 (to HO2S).
The ohmmeter should show 50 ohms to infinite resistance.
If reading is OK:
- Check lead between rear HO2S connector 4 and ECM A34 for signs of short circuiting of the lead between the rear HO2S connector 3 and ECM A19.
If reading is incorrect:
- Test with a new rear HO2S.
INTERMITTENT FAULT, SIGNAL TOO LOW
Checking the Leads And Connectors
NOTE: Rust-removal spray or grease may not be used on the HO2S connector.
^ Check lead between rear HO2S connector 4 and ECM A34 for signs of an intermittent break.
^ Check lead between rear HO2S connector 3 and ECM A19 for signs of an intermittent break.
^ Check the ECM's and rear HO2S connector for signs of loose connection.
^ Check lead between rear HO2S connector 4 and ECM A34 for signs of intermittent short circuiting to ground.
^ Check the lead between front HO2S connector 3 and ECM A33 and the lead between the rear HO2S connector 3 and ECM A19 for signs of intermittent short circuiting to ground.
INTERMITTENT FAULT, FAULTY SIGNAL
Checking the Leads
^ Check lead between rear HO2S connector 4 and ECM A34 for intermittent short circuiting of lead between rear HO2S connector 3 and ECM A19.