Volkswagen Workshop Service and Repair Manuals > Passat (B3) > Power unit | Diesel direct injection and glow plug system | Self diagnosis, V.A.G Inspection Service | Self diagnosis | Evaluating measured value blocks, engine code AFN

Fuel preparation system Diesel injection > < Evaluating measured value blocks, engine codes 1Z and AHU

Diesel direct injection and glow plug system

Self diagnosis

Evaluating measured value blocks, engine code AFN

Display group 07 with ignition switched on (engine cold and not running)

→ Indicated on display

Read measured value block 7 ⇒

15.4 5C 15.9 5C 16.7 5C


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Fuel temperature	Approx. ambient temperature1)	OK	---
	-5.6 °C	Short circuit or fuel temperature sender -G81 defective	- Check G81 In case of fault the measured value block indicates a fuel temperature of -5.6 °C
2 = No display	---	---	---


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 = Intake air temperature	Approx. ambient temperature1)	OK	---
	Approx. 136.8 °C	Intake manifold temperature sender -G72 defective	- Check G72 => Page 23-51 In case of fault the measured value block indicates a constant intake manifold temperature of ca.136.8 °C
4 = Coolant temperature	Approx. ambient temperature1)	OK	---
	Large deviation from ambient temperature	Short circuit or coolant temperature sender -G62 defective	- Check G62 => Page 23-43 In case of fault the fuel temperature is shown alternately

1) Details of temperature specifications are not possible. When the engine is cold the fuel, intake air and coolant temperatures must equate approximately to ambient temperature. If a temperature deviates noticeably then the relevant sender must be checked.

Display group 00 at idling speed (engine warm, coolant temperature not below 80 °C)

→ Indicated on display:

Read measured value block 0 ⇒

43 56 0 24 90 204 59 155 154 116


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	41...45	OK	---
2 = Commencement of injection	0...88	OK	---
	Above 88		- Continue with check in display group 04, => Page 01-87
3 = Accelerator pedal position	0	OK	---
	Above 0		- Continue with check in display group 02, display zone 2 => Page 01-83


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
4 = Quantity injected	11...45	OK	---
	Below 11 or above 45		- Continue with check in display group 01, => Page 01-81
5 = Intake manifold pressure	No specification1)	---	---
6 = Atmospheric pressure	No specification1)	---	---
7 = Coolant temperature	35...80	OK	---
	Above 80	Engine too cold	- Run engine at increased speed to warm up and repeat check. Continue with check in display group 07, display zone 4 => Page 01-76


Display zone	Display on V.A.G 1551/1552	Possible cause(s) if fault	Fault elimination
8 = Intake manifold temperature	50...182	OK	---
	Below 50 or above 182		- Continue with check in display group 07, display zone 3 => Page 01-76
9 = Fuel temperature	91...201	OK	---
	Below 91 or above 201		- Continue with check in display group 07, display zone 1 => Page 01-76
10 = Mass of air drawn in2)	69...135	OK	---
	Below 69 or above 135		- Continue with check in display group 03 => Page 01-84

1) Displays in display zones 5 and 6 must approximately be the same.

2) The measured values require the exhaust gas recirculation (EGR) to be switched on. The EGR is switched off after approx. 10 or 2 minutes at idling speed, therefore give burst on throttle or restart engine.

Display group 01 at idling speed (engine warm, coolant temperature not below 80 °C)

→ Indicated on display

Read measured value block 1 "

840 rpm 6.5 mg/H 1.480 V 87.3 5C


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	861...945 rpm	OK	---
2 = Quantity injected	2.2...9 mg/H	OK	---
	Below 2.2 mg/H	Injection pump too rich	- Renew injection pump => Page 23-19
	Above 9 mg/H	Engine too cold	- Run engine at increased speed to warm up and repeat check.
		Injection pump too lean	- Renew injection pump => Page 23-19


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 = Voltage from slide valve sender	1.45...1.90 V	OK	---
	Below 1.45 V	Injection pump too rich	- Renew injection pump => Page 23-19
	Above 1.90 V	Engine too cold	- Run engine at increased speed to warm up and repeat check.
		Injection pump too lean	- Renew injection pump => Page 23-19
4 = Coolant temperature	80...110 °C	OK	---
	Below 80 °C	Engine too cold	- Run engine at increased speed to warm up and repeat check.

Display group 02 at idling speed (engine warm, coolant temperature not below 80 °C)

→ Indicated on Display

Read measured value block 2 ⇒

840 rpm 0.0 % 0 1 0 88.4 5C


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	861...945 rpm	OK	---
2 = Accelerator position	0 %	Accelerator pedal not operated: OK	---
	1...100 %	Accelerator pedal position sender -G79 incorrectly adjusted or defective	- Check G-79 and adjust if necessary => Page 23-87
		Wiring open circuit to G79	- Check wiring connections to G79 => Page 23-89
3 = Operating condition	010	OK	---
	111	Air conditioning switched on	- Air conditioning switched off
4 = Coolant temperature	85...110 °C	OK	---

Display group 03 at idling speed (engine warm, coolant temperature not below 80 °C)

→ Indicated on display:

Read measured value block 3 "

840 rpm 290 mg/H 308 mg/H 54 %


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	861...945/min	OK	---
2 = Mass of air drawn in (specified)	230...450 mg/H	OK	---
	Above 450 mg/H	Engine too cold	- Run engine at increased speed, to warm up and repeat check.


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 =	230...450 mg/H	OK	---
Mass of air drawn in (actual)1)	Below 230 mg/H	Excessive exhaust gas recirculation	- Check exhaust gas recirculation and air mass meter function => Page 23-79
		Unmetered air	- Check intake air system for leaks.
	Above 450 mg/H	Engine too cold	- Run engine at increased speed, to warm up and repeat check.
		Insufficient exhaust gas recirculation	- Engine running at idling speed for 10 min., give burst on throttle.
		Air mass meter -G70 defective	- Check exhaust gas recirculation and air mass meter => Page 23-79 In case of fault the measured value block shows a constant air mass value of approx. 555 mg/H over the complete speed and throttle range.


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
4 = Duty cycle from exhaust gas recirculation valve	10...90 %	OK	---

1) The measured values require the exhaust gas recirculation (EGR) to be switched on. The EGR is switched off after approx.10 or 2 minutes at idling speed, therefore give burst on throttle or restart engine.

Display group 04 at idling speed (engine warm, coolant temperature not below 80 °C)

→ Indicated on Display

Read measured value block 4 ⇒

900 rpm 0.95 BTDC 1.25 BTDC 4 %


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	861...945 rpm	OK	---
2 = Commencement of injection (specified)	2° ATDC... 4° BTDC	OK	---
	Above 4° BTDC	Engine too cold	- Run engine at increased speed to warm up and repeat check.


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 = Commencement of injection (actual)	2° ATDC... 4° BTDC	OK	---
	Above 4° BTDC	Engine too cold	- Run engine at increased speed to warm up and repeat check.
		Injection pump positioned "early"	- Check and adjust commencement of injection dynamically => Page 23-24
		Commencement of injection valve -N108 defective	- Check -N 108 => Page 01-35 , final control diagnosis
	Retarded 2° ATDC	Injection pump positioned extremely "retarded"	- Check and adjust commencement of injection dynamically => Page 23-24
		Injection adjustment blocked	- Check -N108 => Page 01-35 , final control diagnosis
		Commencement of injection valve -N108 defective
4 = Duty cycle from commencement of injection valve	2...95 %	OK	---

Display group 13 at idling speed (engine warm, coolant temperature not below 80 °C)

→ Indicated on display:

Read measured value block 13 ⇒

0.82mg/H -0.12mg/H 0.49mg/H

The injection system is equipped with an idling speed smooth running control. There may be power differences between the individual cylinders (component tolerances, jet drillings, compressions etc.) which are recognised and equalized via selective injected quantities.

Recognition at idling speed is via the signal from the engine speed sender which delivers four signals per crankshaft revolution to the control unit. If the signals are delivered at the same rhythm then all cylinders work the same. If one cylinder is weaker then the crankshaft takes longer for the next half revolution. Conversely a more powerful cylinder accelerates the crankshaft so less time is taken.

If the control unit recognises a difference, then the relevant cylinder is given more or less fuel, until the engine runs evenly again.

The measured value block displays the injected quantity differences of the individual cylinders compared with No. 3 cylinder that is required to ensure an even engine idling speed.

+... mg/H: The relevant cylinder is less powerful than No. 3 cylinder and is therefore supplied with more fuel.

-... mg/H: The relevant cylinder is more powerful than No. 3 cylinder and is therefore supplied with less fuel.

Display group 00 at full throttle (test drive in 3rd gear, coolant temperature not below 80 °C)

Notes:

◆ When testing, accelerate vehicle at full throttle.
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.

→ Indicated on display

Read measured value block 0 ⇒

148 157 255 123 91 205 68 151 157 154


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	136...150	OK	---
	Above 190	Revolutions too high, engine governed	--
2 = Commencement of injection	138...188	OK	---
	Below 138		- Continue with check in display group 04, => Page 01-93


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 = Accelerator pedal position	255	OK	---
	Below 255	Not at full throttle	- Repeat check at full throttle.
4 = Quantity injected	192...215	OK	---
	Below 192		- Continue with check in display group 08, => Page 01-95
5 = Intake manifold pressure	180...245	OK
	Below 180 or above 245		- Continue with check in display group 11, => Page 01-99
6 = Atmospheric pressure	No specification	---	---


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
7 = Coolant temperature	35...80	OK	---
	Above 80	Engine too cold	- Continue with check in display group 07, display zone 4
8 = Intake air temperature	50...182	OK	---
	Below 50 or above 182		- Continue with check in display group 07, display zone 3
9 = Fuel temperature	91...201	OK	---
	Below 91 or above 201		- Continue with check in display group 07, display zone 1 => Page 01-76
10 = Mass of air drawn in	225...255	OK	---
	Below 225		- Continue with check in display group 10, display zone 1 => Page 01-97

Display group 04 at full throttle (test drive in 3rd gear, coolant temperature not below 80 °C)

Notes:

◆ When testing, accelerate vehicle at full throttle.
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.

→ Indicated on display:

Read measured value block 4 "

3100 rpm 105 BTDC 105 BTDC 80 %


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	2850...3150/min	OK	---
2 = Commencement of injection (specified)	8...12 ° BTDC	OK	---


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 = Commencement of injection (actual)	Approx. commencement of injection (specified)	OK	---
	For large differences between specified and actual (approx. 5 ° crank angle)	Commencement of injection valve -N108 defective Injection pump positioned incorrectly Air in fuel system	- Check -N108 => Page 23-24 Check fuel supply system
4 = Duty cycle from commencement of injection valve	60...98 %	OK	---
	Below 60 or above 98 %	Commencement of injection valve -N108 defective	- Check -N108 => Page 23-24 Check fuel supply system

Display group 08 at full throttle (test drive in 3rd gear, coolant temperature not below 80 °C)

Notes:

◆ When testing, accelerate vehicle at full throttle.
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.

→ Indicated on display

Read measured value block 8 ⇒

3290 rpm 38.4 mg/H 35.2 mg/H 35.7 mg/H


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	2850...3150 rpm	OK	---
2 = Quantity injected (driver's requirement)	43...45 mg/H	OK	---
	Below 43 mg/H	Not full throttle	- Repeat check at full throttle.
		Accelerator pedal position sender -G79 incorrectly adjusted or defective	- Check G-79 and if necessary adjust => Page 23-87


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 = Quantity injected (torque map)	40...42 mg/H	OK	---
	Below 40 mg/H	Speed too high or too low	---
4 = Quantity injected (opacity map)	38.5...44 mg/H	OK	---
	Below 38.5 mg/H	Mass of air drawn in too low	- Check exhaust gas recirculation and air mass meter function => Page 23-79
		Quantity of exhaust gas recirculated	- Check exhaust gas recirculation and air mass meter => Page 23-79

Display group10 at full throttle (test drive in 3rd gear, coolant temperature not below 80 °C)

Notes:

◆ When testing, accelerate the vehicle at full throttle.
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.

→ Indicated on display:

Read measured value block 10 "

830 mg/H 1030 mbar 1850 mbar 100 %


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Mass of air drawn in (actual)	850...1050 mg/H	OK	---
	Below 850 mg/H	Speed too low or too high	- Read off specification at 3000 rpm.
		Charge pressure too low	- Check charge pressure control => Page 23-67
		Air mass meter defective	- Check exhaust gas recirculation and air mass meter function => Page 23-79 In case of fault the measured value block shows a constant air mass value of about 550 mg/H over complete speed and throttle range


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
2 = Atmospheric pressure (air pressure)	No specification	---	---
3 =	1700...2500 mbar	OK	---
Intake manifold pressure (charge pressure)	Below 1700 mbar	Charge pressure control defective	- Check charge pressure control => Page 23-67
		Turbocharger defective
	Above 2500 mbar
4 =	100 %	OK	---
Accelerator pedal position	Below 100 %	Not full throttle	- Repeat check at full throttle.
		Accelerator pedal position sender -G79 incorrectly adjusted or defective	- Check G-79 and if necessary adjust => Page 23-87

Display group 11 at full throttle (test drive in 3rd gear, coolant temperature not below 80 °C)

Notes:

◆ When testing, accelerate the vehicle at full throttle.
◆ The measured values must be printed out or read (2nd person required) when the revolutions reach 3,000 rpm.

→ Indicated on display:

Read measured value block 11 "

3340 rpm 1830 mbar 1850 mbar 68 %


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
1 = Engine speed	2850...3150 rpm	OK	---
2 = Charge pressure (specified)	1900...2000 mbar	OK	---


Display zone	Display on V.A.G 1551/1552	Possible cause(s) of fault	Fault remedy
3 = Charge pressure (actual)	1700...2500 mbar	OK	---
	Below 1700 mbar	Charge pressure control defective	- Check charge pressure control => Page 23-67
		Turbocharger defective
		Charge pressure hose not connected to control unit	- Connect charge pressure hose
	Above 2500 mbar	Turbocharger defective	- Check charge pressure control => Page 23-67
4 = Duty cycle from charge pressure control valve	45...94 %	OK	---

Power unit
Diesel direct injection and glow plug system / Self diagnosis, V.A.G Inspection Service / Self diagnosis
Evaluating measured value blocks, engine code AFN

Fuel preparation system Diesel injection > < Evaluating measured value blocks, engine codes 1Z and AHU

Volkswagen Workshop Service and Repair Manuals

Passat (B3)

Power unit Diesel direct injection and glow plug system / Self diagnosis, V.A.G Inspection Service / Self diagnosis Evaluating measured value blocks, engine code AFN

Power unit Diesel direct injection and glow plug system / Self diagnosis, V.A.G Inspection Service / Self diagnosis Evaluating measured value blocks, engine code AFN

Power unit
Diesel direct injection and glow plug system / Self diagnosis, V.A.G Inspection Service / Self diagnosis
Evaluating measured value blocks, engine code AFN

Power unit
Diesel direct injection and glow plug system / Self diagnosis, V.A.G Inspection Service / Self diagnosis
Evaluating measured value blocks, engine code AFN