Low voltage O2 sensor CEL, Low Idle - HELP
#1
08-19-2009, 04:22 AM
Low voltage O2 sensor CEL, Low Idle - HELP
I have a CEL and nobody seems to be able to figure out what's causing it. The car is 1998.5 A4, 2.8Q, manual.
At first pulled the codes and diagnosed as:
17606 - Oxygen Sensor Heater circuit: B1S2 Electrical Malfunction, intermittent.
17607 - Oxygen Sensor Heater circuit: b2S2: electrical Malfunction, intermittent
16544 - Oxygen Sensor B2S2: No activity, intermittent
Cleared the codes and recommended drive and see if fault recurs.
The CEL came back on the next morning. cleared the code and advised to drive the car a few more days.
The CEL came back the same day after I drove off. mechanic advised I can drive for a few weeks with the CEL. 2 weeks later I took it in again to fix the problem.
They replaced both rear O2 sensors and forced readiness. Next morning the CEL came back on. Checked and recorded fault codes 16541: O2 sensor B2S2 signal too low; 16501 Engine coolant temp signal too low. put in a new set of rear O2 sensors. Deoxit connectors at all O2 sensors. Replaced engine management coolant temp sensor plus water temp sensor O-ring.
Five minutes after starting the car the CEL came back on. multiple fault codes were stored. Detected low signal from all oxygen sensors, engine coolant temp sensor, and intake air temp sensor. Voltage fluctuating at Oxygen sensors, but no voltage at data block reading. voltage not fluctuating properly, may be attempting to compensate for inaccuracies in air fuel ratios.
did testing electrical wiring between O2 sensors and ECU. Attempt to force readiness failed. Test voltage supply at (G39) B1S2 and (G108) B2S2. Obtained 0.44V at both (spec 0.4-0.5V).
Test wiring resistance from ECU J220 to G39, (spec is 1.5 ohms max).
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Test resistance from J220 (T121) to (G108):
Pin 39 (T121) to Pin 3 9G108) 0.2 ohm
Pin 40 (T121) to Pin 4 9G108) 0.3 ohm
All post CAT O2 wiring tested within spec.
Tested ECM (J200) supply voltage when running and voltage stayed at 13.46V.
installed another ECU and got the same fault codes.
At this point I took the car to Audi. They pulled the following codes:
P1602 - Power supply Terminal 30 Low voltage sporadic.
P0131 - O2 sensor Circ. B1S1 Low voltage, sporadic.
P0151 - O2Sensor Circ. B2S1 low voltage sporadic.
P0117 - Engine coolant temp sensor 1 circuit low sporadic
P0137 - O2 sensor circ B1S2 low voltage.
P0112 - intake air pump circ low input sporadic.
P1128 - long term fuel trim mult bank2 system too lean sporadic.
Inspected vacuum lines for leaks. Noticed water pump making noise while idling. suspect thermostat could be stuck causing erratic O2 readings. Replaced spark plugs. Attempt to set readiness codes failed due to codes reappearing during procedure (P0117 engine coolant temp sensor 1 circuit low sporadic, P0137 O2 sensor circ B1S2 low voltage sporadic, P0157 O2 sensor circ B2S2 low voltage). Checked MVB 1 and 2 for MAF and coolant readings. Noticed values kept fluctuating from very low to very high. Checked O2 sensor readings in MVB 33. Also found values fluctuating from 0.02V - 0.7V. Removed connector for ECT and installed known good ECT for testing. Rechecked values at idle and found coolant temp readings still fluctuating. Contacted TAC. Advised to perform wire checks on all circuits. Performed electrical checks of wiring for IAT sensor, ECT and reat O2 sensors. Resitance well within spec, under 1.5 ohms. Checked for short to ground and short to power on wires. Wiring between components and ECM good. Checked ground for ECM, verified secure. Inspected relay below driver's under panel. Contacted TAC for info - advised to check power and ground at ECM before and after. Readings remained stable. Noticed vehicle ran smooth with MAF unplugged. This causes ECM to run on preset values. Updated TAC with info. Advised to replace ECM due to being faulty.
I bought a ECM from a dismantler. installed and still get the CEL on within about 2 miles of driving. Then yesterday, after sticking the ECM with cleared codes in the car I drove about 150 miles (mostly freeway driving) with the CEL off. I thought a miracle happened and it was fixed, but when I got into town and pulled into the driveway the CEL came back on.
Lately, I have noticed that the car has really low idle speed, usually dropping below 500 rpm then recovering. If stopped at a light sometimes idle drops to below 200 and sometimes the car dies. Also, if I park and bring the RPMs to about 2000 and suddenly let go of the accelerator the rpms drop to around 200 or sometimes below then recover to about 600-700. If the car dies when I stop at a traffic light (which has happened a few times) it is usually really hard to start it up again (takes 5-10 seconds of crancking to finally start).
I reset the codes again today and the faults that came back are:
16521 - B1S2 signal too low.
16541 - B2S2 signal too low.
16496 - intake air temp sensor, signal too low.
16501 - engine coolant temp. sensor, signal too low.
Thank you in advance!
At first pulled the codes and diagnosed as:
17606 - Oxygen Sensor Heater circuit: B1S2 Electrical Malfunction, intermittent.
17607 - Oxygen Sensor Heater circuit: b2S2: electrical Malfunction, intermittent
16544 - Oxygen Sensor B2S2: No activity, intermittent
Cleared the codes and recommended drive and see if fault recurs.
The CEL came back on the next morning. cleared the code and advised to drive the car a few more days.
The CEL came back the same day after I drove off. mechanic advised I can drive for a few weeks with the CEL. 2 weeks later I took it in again to fix the problem.
They replaced both rear O2 sensors and forced readiness. Next morning the CEL came back on. Checked and recorded fault codes 16541: O2 sensor B2S2 signal too low; 16501 Engine coolant temp signal too low. put in a new set of rear O2 sensors. Deoxit connectors at all O2 sensors. Replaced engine management coolant temp sensor plus water temp sensor O-ring.
Five minutes after starting the car the CEL came back on. multiple fault codes were stored. Detected low signal from all oxygen sensors, engine coolant temp sensor, and intake air temp sensor. Voltage fluctuating at Oxygen sensors, but no voltage at data block reading. voltage not fluctuating properly, may be attempting to compensate for inaccuracies in air fuel ratios.
did testing electrical wiring between O2 sensors and ECU. Attempt to force readiness failed. Test voltage supply at (G39) B1S2 and (G108) B2S2. Obtained 0.44V at both (spec 0.4-0.5V).
Test wiring resistance from ECU J220 to G39, (spec is 1.5 ohms max).
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Test resistance from J220 (T121) to (G108):
Pin 39 (T121) to Pin 3 9G108) 0.2 ohm
Pin 40 (T121) to Pin 4 9G108) 0.3 ohm
All post CAT O2 wiring tested within spec.
Tested ECM (J200) supply voltage when running and voltage stayed at 13.46V.
installed another ECU and got the same fault codes.
At this point I took the car to Audi. They pulled the following codes:
P1602 - Power supply Terminal 30 Low voltage sporadic.
P0131 - O2 sensor Circ. B1S1 Low voltage, sporadic.
P0151 - O2Sensor Circ. B2S1 low voltage sporadic.
P0117 - Engine coolant temp sensor 1 circuit low sporadic
P0137 - O2 sensor circ B1S2 low voltage.
P0112 - intake air pump circ low input sporadic.
P1128 - long term fuel trim mult bank2 system too lean sporadic.
Inspected vacuum lines for leaks. Noticed water pump making noise while idling. suspect thermostat could be stuck causing erratic O2 readings. Replaced spark plugs. Attempt to set readiness codes failed due to codes reappearing during procedure (P0117 engine coolant temp sensor 1 circuit low sporadic, P0137 O2 sensor circ B1S2 low voltage sporadic, P0157 O2 sensor circ B2S2 low voltage). Checked MVB 1 and 2 for MAF and coolant readings. Noticed values kept fluctuating from very low to very high. Checked O2 sensor readings in MVB 33. Also found values fluctuating from 0.02V - 0.7V. Removed connector for ECT and installed known good ECT for testing. Rechecked values at idle and found coolant temp readings still fluctuating. Contacted TAC. Advised to perform wire checks on all circuits. Performed electrical checks of wiring for IAT sensor, ECT and reat O2 sensors. Resitance well within spec, under 1.5 ohms. Checked for short to ground and short to power on wires. Wiring between components and ECM good. Checked ground for ECM, verified secure. Inspected relay below driver's under panel. Contacted TAC for info - advised to check power and ground at ECM before and after. Readings remained stable. Noticed vehicle ran smooth with MAF unplugged. This causes ECM to run on preset values. Updated TAC with info. Advised to replace ECM due to being faulty.
I bought a ECM from a dismantler. installed and still get the CEL on within about 2 miles of driving. Then yesterday, after sticking the ECM with cleared codes in the car I drove about 150 miles (mostly freeway driving) with the CEL off. I thought a miracle happened and it was fixed, but when I got into town and pulled into the driveway the CEL came back on.
Lately, I have noticed that the car has really low idle speed, usually dropping below 500 rpm then recovering. If stopped at a light sometimes idle drops to below 200 and sometimes the car dies. Also, if I park and bring the RPMs to about 2000 and suddenly let go of the accelerator the rpms drop to around 200 or sometimes below then recover to about 600-700. If the car dies when I stop at a traffic light (which has happened a few times) it is usually really hard to start it up again (takes 5-10 seconds of crancking to finally start).
I reset the codes again today and the faults that came back are:
16521 - B1S2 signal too low.
16541 - B2S2 signal too low.
16496 - intake air temp sensor, signal too low.
16501 - engine coolant temp. sensor, signal too low.
Thank you in advance!
Last edited by idvn; 08-20-2009 at 06:45 PM. Reason: update
#2
12-06-2009, 08:00 PM
I have a CEL and nobody seems to be able to figure out what's causing it. The car is 1998.5 A4, 2.8Q, manual.
At first pulled the codes and diagnosed as:
17606 - Oxygen Sensor Heater circuit: B1S2 Electrical Malfunction, intermittent.
17607 - Oxygen Sensor Heater circuit: b2S2: electrical Malfunction, intermittent
16544 - Oxygen Sensor B2S2: No activity, intermittent
Cleared the codes and recommended drive and see if fault recurs.
The CEL came back on the next morning. cleared the code and advised to drive the car a few more days.
The CEL came back the same day after I drove off. mechanic advised I can drive for a few weeks with the CEL. 2 weeks later I took it in again to fix the problem.
They replaced both rear O2 sensors and forced readiness. Next morning the CEL came back on. Checked and recorded fault codes 16541: O2 sensor B2S2 signal too low; 16501 Engine coolant temp signal too low. put in a new set of rear O2 sensors. Deoxit connectors at all O2 sensors. Replaced engine management coolant temp sensor plus water temp sensor O-ring.
Five minutes after starting the car the CEL came back on. multiple fault codes were stored. Detected low signal from all oxygen sensors, engine coolant temp sensor, and intake air temp sensor. Voltage fluctuating at Oxygen sensors, but no voltage at data block reading. voltage not fluctuating properly, may be attempting to compensate for inaccuracies in air fuel ratios.
did testing electrical wiring between O2 sensors and ECU. Attempt to force readiness failed. Test voltage supply at (G39) B1S2 and (G108) B2S2. Obtained 0.44V at both (spec 0.4-0.5V).
Test wiring resistance from ECU J220 to G39, (spec is 1.5 ohms max).
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Test resistance from J220 (T121) to (G108):
Pin 39 (T121) to Pin 3 9G108) 0.2 ohm
Pin 40 (T121) to Pin 4 9G108) 0.3 ohm
All post CAT O2 wiring tested within spec.
Tested ECM (J200) supply voltage when running and voltage stayed at 13.46V.
installed another ECU and got the same fault codes.
At this point I took the car to Audi. They pulled the following codes:
P1602 - Power supply Terminal 30 Low voltage sporadic.
P0131 - O2 sensor Circ. B1S1 Low voltage, sporadic.
P0151 - O2Sensor Circ. B2S1 low voltage sporadic.
P0117 - Engine coolant temp sensor 1 circuit low sporadic
P0137 - O2 sensor circ B1S2 low voltage.
P0112 - intake air pump circ low input sporadic.
P1128 - long term fuel trim mult bank2 system too lean sporadic.
Inspected vacuum lines for leaks. Noticed water pump making noise while idling. suspect thermostat could be stuck causing erratic O2 readings. Replaced spark plugs. Attempt to set readiness codes failed due to codes reappearing during procedure (P0117 engine coolant temp sensor 1 circuit low sporadic, P0137 O2 sensor circ B1S2 low voltage sporadic, P0157 O2 sensor circ B2S2 low voltage). Checked MVB 1 and 2 for MAF and coolant readings. Noticed values kept fluctuating from very low to very high. Checked O2 sensor readings in MVB 33. Also found values fluctuating from 0.02V - 0.7V. Removed connector for ECT and installed known good ECT for testing. Rechecked values at idle and found coolant temp readings still fluctuating. Contacted TAC. Advised to perform wire checks on all circuits. Performed electrical checks of wiring for IAT sensor, ECT and reat O2 sensors. Resitance well within spec, under 1.5 ohms. Checked for short to ground and short to power on wires. Wiring between components and ECM good. Checked ground for ECM, verified secure. Inspected relay below driver's under panel. Contacted TAC for info - advised to check power and ground at ECM before and after. Readings remained stable. Noticed vehicle ran smooth with MAF unplugged. This causes ECM to run on preset values. Updated TAC with info. Advised to replace ECM due to being faulty.
I bought a ECM from a dismantler. installed and still get the CEL on within about 2 miles of driving. Then yesterday, after sticking the ECM with cleared codes in the car I drove about 150 miles (mostly freeway driving) with the CEL off. I thought a miracle happened and it was fixed, but when I got into town and pulled into the driveway the CEL came back on.
Lately, I have noticed that the car has really low idle speed, usually dropping below 500 rpm then recovering. If stopped at a light sometimes idle drops to below 200 and sometimes the car dies. Also, if I park and bring the RPMs to about 2000 and suddenly let go of the accelerator the rpms drop to around 200 or sometimes below then recover to about 600-700. If the car dies when I stop at a traffic light (which has happened a few times) it is usually really hard to start it up again (takes 5-10 seconds of crancking to finally start).
I reset the codes again today and the faults that came back are:
16521 - B1S2 signal too low.
16541 - B2S2 signal too low.
16496 - intake air temp sensor, signal too low.
16501 - engine coolant temp. sensor, signal too low.
Thank you in advance!
At first pulled the codes and diagnosed as:
17606 - Oxygen Sensor Heater circuit: B1S2 Electrical Malfunction, intermittent.
17607 - Oxygen Sensor Heater circuit: b2S2: electrical Malfunction, intermittent
16544 - Oxygen Sensor B2S2: No activity, intermittent
Cleared the codes and recommended drive and see if fault recurs.
The CEL came back on the next morning. cleared the code and advised to drive the car a few more days.
The CEL came back the same day after I drove off. mechanic advised I can drive for a few weeks with the CEL. 2 weeks later I took it in again to fix the problem.
They replaced both rear O2 sensors and forced readiness. Next morning the CEL came back on. Checked and recorded fault codes 16541: O2 sensor B2S2 signal too low; 16501 Engine coolant temp signal too low. put in a new set of rear O2 sensors. Deoxit connectors at all O2 sensors. Replaced engine management coolant temp sensor plus water temp sensor O-ring.
Five minutes after starting the car the CEL came back on. multiple fault codes were stored. Detected low signal from all oxygen sensors, engine coolant temp sensor, and intake air temp sensor. Voltage fluctuating at Oxygen sensors, but no voltage at data block reading. voltage not fluctuating properly, may be attempting to compensate for inaccuracies in air fuel ratios.
did testing electrical wiring between O2 sensors and ECU. Attempt to force readiness failed. Test voltage supply at (G39) B1S2 and (G108) B2S2. Obtained 0.44V at both (spec 0.4-0.5V).
Test wiring resistance from ECU J220 to G39, (spec is 1.5 ohms max).
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Pin 25 (T121) to Pin 3 (G39) 0.3 ohm
Test resistance from J220 (T121) to (G108):
Pin 39 (T121) to Pin 3 9G108) 0.2 ohm
Pin 40 (T121) to Pin 4 9G108) 0.3 ohm
All post CAT O2 wiring tested within spec.
Tested ECM (J200) supply voltage when running and voltage stayed at 13.46V.
installed another ECU and got the same fault codes.
At this point I took the car to Audi. They pulled the following codes:
P1602 - Power supply Terminal 30 Low voltage sporadic.
P0131 - O2 sensor Circ. B1S1 Low voltage, sporadic.
P0151 - O2Sensor Circ. B2S1 low voltage sporadic.
P0117 - Engine coolant temp sensor 1 circuit low sporadic
P0137 - O2 sensor circ B1S2 low voltage.
P0112 - intake air pump circ low input sporadic.
P1128 - long term fuel trim mult bank2 system too lean sporadic.
Inspected vacuum lines for leaks. Noticed water pump making noise while idling. suspect thermostat could be stuck causing erratic O2 readings. Replaced spark plugs. Attempt to set readiness codes failed due to codes reappearing during procedure (P0117 engine coolant temp sensor 1 circuit low sporadic, P0137 O2 sensor circ B1S2 low voltage sporadic, P0157 O2 sensor circ B2S2 low voltage). Checked MVB 1 and 2 for MAF and coolant readings. Noticed values kept fluctuating from very low to very high. Checked O2 sensor readings in MVB 33. Also found values fluctuating from 0.02V - 0.7V. Removed connector for ECT and installed known good ECT for testing. Rechecked values at idle and found coolant temp readings still fluctuating. Contacted TAC. Advised to perform wire checks on all circuits. Performed electrical checks of wiring for IAT sensor, ECT and reat O2 sensors. Resitance well within spec, under 1.5 ohms. Checked for short to ground and short to power on wires. Wiring between components and ECM good. Checked ground for ECM, verified secure. Inspected relay below driver's under panel. Contacted TAC for info - advised to check power and ground at ECM before and after. Readings remained stable. Noticed vehicle ran smooth with MAF unplugged. This causes ECM to run on preset values. Updated TAC with info. Advised to replace ECM due to being faulty.
I bought a ECM from a dismantler. installed and still get the CEL on within about 2 miles of driving. Then yesterday, after sticking the ECM with cleared codes in the car I drove about 150 miles (mostly freeway driving) with the CEL off. I thought a miracle happened and it was fixed, but when I got into town and pulled into the driveway the CEL came back on.
Lately, I have noticed that the car has really low idle speed, usually dropping below 500 rpm then recovering. If stopped at a light sometimes idle drops to below 200 and sometimes the car dies. Also, if I park and bring the RPMs to about 2000 and suddenly let go of the accelerator the rpms drop to around 200 or sometimes below then recover to about 600-700. If the car dies when I stop at a traffic light (which has happened a few times) it is usually really hard to start it up again (takes 5-10 seconds of crancking to finally start).
I reset the codes again today and the faults that came back are:
16521 - B1S2 signal too low.
16541 - B2S2 signal too low.
16496 - intake air temp sensor, signal too low.
16501 - engine coolant temp. sensor, signal too low.
Thank you in advance!
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