catalytic converter AUDI A4 1998 B5 / 1.G APB Engine Motronic Syst

01-3

Exhaust Malfunction Indicator Light
(MIL), significance

If the Engine Control Module (ECM) recognizes
emission related malfunctions, this is indicates by
the MIL coming on.

Component location of MIL
Note:
When a recognized malfunction switches on the MIL, it will either blink or
light continuously. In either case, the DTC memory must be checked
Page 01
-15
.
If the MIL starts to blink, there is a malfunction that can lead to damage of
the Three Way Catalytic Converter (TWC). In this case driving should be
only continue with reduced power until the MIL goes out or stays on
continuously.
Continuos MIL
If the MIL lights continuously, there is malfunction that affects exhaust
emissions. In this case the DTC memory of the ECM and Transmission
Control Module (TCM) (if equipped) must be checked.
Some malfunctions may occur without causing the MIL to come on. When
driveability or performance problems are reported and there is no
indication from the MIL, the operation of the MIL must be checked. In
addition, the DTC memory of the ECM and TCM must be checked, as
there may be malfunctions stored that do not switch the MIL on
immediately.
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01-23

DTC
Description of
malfunction
Corrective action
SAE
VAG


P0136 16520 02 Sensor Circ., Bank1-
Sensor2
Malfunction
2) - Check oxygen sensor heater Page 24
-114
P0137 16521 02 Sensor Circ., Bank1-
Sensor2
Low Voltage
2) - Check oxygen sensor signal wire and activation Page 24
-122
P0138 16522 02 Sensor Circ., Bank1-
Sensor2
High Voltage
2)
P0139 16523 02 Sensor Circ., Bank1-
Sensor2
Slow Response2) - Check oxygen sensor and oxygen sensor control behind catalytic
converter Page 24
-100

P0140 16524 02 Sensor Circ., Bank1-
Sensor2
No Activity Detected
2)
2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
Pa
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01-25

DTC
Description of
malfunction
Corrective action
SAE
VAG


P0156 16540 02 Sensor Circ., Bank2-
Sensor2
Malfunction
2) - Check oxygen sensor heater Page 24
-114
P0157 16541 02 Sensor Circ., Bank2-
Sensor2
Low Voltage
2) - Check oxygen sensor signal wire and activation Page 24
-122
P0158 16542 02 Sensor Circ., Bank2-
Sensor2
High Voltage
2)
P0159 16543 02 Sensor Circ., Bank2-
Sensor2
Slow Response 2) - Check oxygen sensor and oxygen sensor control behind catalytic
converter Page 24
-100

P0160 16544 02 Sensor Circ., Bank2-
Sensor2
No Activity Detected
2) - Check oxygen sensor heater Page 24
-114
2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
Pa
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01-27

DTC
Description of malfunction
Corrective action
SAE
VAG


P0300 16684 Random/Multiple Cylinder
Misfire Detected
2) - Check cause for misfire Page 28
-52
P0301 16685
Cyl.1 Misfire Detected
2)
- Check fuel tank level
P0302 16686
Cyl.2 Misfire Detected 2)

P0303 16687
Cyl.3 Misfire Detected 2)

P0304 16688
Cyl.4 Misfire Detected 2)

P0305 16689
Cyl.5 Misfire Detected 2)

P0306 16690
Cyl.6 Misfire Detected 2)

2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
The Malfunction Indicator Light (MIL) will blink if the Engine Control Module (ECM) recognizes misfire that could damage the
catalytic converters.
Notes:

On malfunction which could be caused by lack of fuel (e.g.: misfire) the malfunction P1250 "Fuel level too low" will be
displayed in addition. That means, the misfiring was detected due to lack of fuel in the tank and not due to a technical
malfunction.
Pa
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01-29

DTC
Description of
malfunction
Corrective action
SAE
VAG


P0421 16805 Warm Up Catalyst,
Bank 1
Efficiency Below
Threshold
2) Repair Manual, 2.7 Liter V6 5V BiTurbo Engine Mechanical, Repair Group 26;
Components of Exhaust system removing and installing, Catalytic converter
removing and installing - Generate readiness code Page 01
-99
, if same DTC is displayed again, replace
warm up catalytic converter bank 1
P0431 16815 Warm Up Catalyst,
Bank 2
Efficiency Below
Threshold
2) Repair Manual, 2.7 Liter V6 5V BiTurbo Engine Mechanical, Repair Group 26;
Components of Exhaust system removing and installing, Catalytic converter
removing and installing - Generate readiness code Page 01
-99
, if same DTC is displayed again, replace
warm up catalytic converter bank 1
2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
Important note:
The warm up catalytic converters are located between the two oxygen sensors of the relevant cylinder bank. The warm up
catalytic converters (little smaller than main catalytic converter) are located closer to the engine, not to be misunderstood with
the main catalysts you see immediately once the vehicle is lifted.
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01-36

DTC
Description of malfunction
Corrective action
SAE
VAG


P1127 17535 Long Term Fuel Trim mult., Bank1
System too rich
2) - Carry out road test (Fuel in engine oil)
- Check fuel pressure Page 24
-33
P1128 17536 Long Term Fuel Trim mult., Bank1
System too lean
2) - Check Mass Air Flow (MAF) Sensor Page 24
-59
- Check for unmetered (false) air Page 24
-76
P1129 17537 Long Term Fuel Trim mult., Bank2
System too rich
2) - Check oxygen sensor before catalytic converter Page 24
-81
- Check oxygen sensor behind catalytic converter Page 24
-100
P1130 17538 Long Term Fuel Trim mult., Bank2
System too lean
2) - Check fuel injectors Page 24
-43
P1131 17539 Bank2-Sensor1
Internal Resistance too High
2) - Check oxygen sensor heater Page 24
-114
.
- Check oxygen sensor signal wire and activation Page 24
-122
2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
Note:
mult. = multiplikative means that the malfunction affects the entire RPM and load range.
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01-37

DTC
Description of malfunction
Corrective action
SAE
VAG


P1136 17544 Long Term Fuel Trim Add. Fuel,
Bank1
System too Lean
2) - Carry out road test (fuel in engine oil)
P1137 17545 Long Term Fuel Trim Add. Fuel,
Bank1
System too Rich
2) - Check fuel pressure Page 24
-33
P1138 17546 Long Term Fuel Trim Add. Fuel,
Bank2
System too Lean
2) - Check Mass Air Flow (MAF) Sensor Page 24
-59
P1139 17547 Long Term Fuel Trim Add. Fuel,
Bank2
System too Rich
2) - Check oxygen sensor before catalytic converter Page 24
-81
- Check oxygen sensor behind catalytic converter Page 24
-
100

- Check EVAP canister valve 1 Page 24
-134
P1140 17548 Bank2-Sensor2
Internal Resistance too High
2) - Check oxygen sensor heater Page 24
-114
.
- Check oxygen sensor signal wire and activation Page 24
-
122

2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
Pa
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01-39

DTC
Description of malfunction
Corrective action
SAE
VAG


P1171 17579 Throttle Actuation Potentiometer
Signal 2
Range/Performance
1) 3)
- Check throttle actuation potentiometer Page 24
-153
.
P1172 17580 Throttle Actuation Potentiometer
Signal 2
Signal too Low
1) 3)


P1173 17581 Throttle Actuation Potentiometer
Signal 2
Signal too High
1) 3)


P1176 17584 O2 Correction Behind Catalyst, B1
Limit Attained
2) - Check oxygen sensor aging of oxygen sensors before catalytic
converters Page 24
-93

P1177 17585 O2 Correction Behind Catalyst, B2
Limit Attained
2) - Check oxygen sensors and
oxygen sensor control behind catalytic converters Page 24
-100
1) With this malfunction the EPC (Electronic Power Control) Malfunction Indicator Light (MIL) in the instrument cluster is
switched on by the ECM immediately after the malfunction has been recognized. Significance of EPC malfunction indicator
light Page 24
-142
.
2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
Pa
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01-74

DTC
Description of malfunction
Corrective action
SAE
VAG


P1851 18259 Data Bus Powertrain
Missing Message from Brake Contr
Repair Manual, Brake System On Board Diagnostic (OBD), Repair
Group 01, checking DTC memory of ABS control module
- Check DTC memory of ABS control module
- Check data exchange between Engine-/ABS-
/Transmission control
module Page 24
-201

P1853 18261 Data Bus Powertrain
Unplausible Message from Brake
Contr.
P1854 18262 Data Bus Powertrain
Hardware Defective
P3262 19718 Exhaust bank 1/2 oxygen sensors
behind catalytic converter
mixed up - Check harness connectors for oxygen sensors and check installed
position of oxygen sensors behind catalytic converter. 1) With this malfunction the EPC (Electronic Power Control) Malfunction Indicator Light (MIL) in the instrument cluster is
switched on by the ECM. Significance of EPC malfunction indicator light Page 24
-142
.
2) With this malfunction the exhaust Malfunction Indicator Light (MIL) is only switched on by the ECM, if the malfunction is
recognized after the engine has been restarted. Significance of MIL Page 01
-3 .
Pa
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01-103

X
X
X
X
X
X
X
X
Notes for display group 086 display field 1 (Ready-Bits)

1 = Three Way Catalytic Converter (TWC) (diagnostic of catalytic converter)

Display 0 = ready
Display 1 = not ready (Readiness code generating Page 01
-105
)

2 = TWC Catalytic Converter (not available/always "0")

3 = EVAP system (0 = ready)

Display 0 = ready
Display 1 = not ready (Readiness code generating Page 01
-105
)

4 = Secondary Air Injection (AIR) System

Display 0 = ready
Display 1 = not ready (Readiness code generating Page 01
-105
)

5 = Climate Control (diagnosis not applicable/always "0")

6 = Oxygen sensors

Display 0 = ready
Display 1 = not ready (Readiness code generating Page 01
-105
)

7 = Oxygen sensor (O2S) heater

Display 0 = ready
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