A Comprehensive On-Board Diagnostic (OBD) Trouble Code List for the Porsche 993 and what they mean.

Disclaimer:  The author here is not a professional automotive technician and some information on this page may not be accurate in all situations and may be in some cases different from official factory information.  Although we strive to provide completely accurate and appropriate information and we attempt to keep it up to date, in some cases, some of the information you find on this page may be outdated or in error therefore, please feel free to use the information on this page at your own risk. We encourage you to contact us with any errors or omissions you may find on this page at andrew.hess@differentlight.biz so we may make any corrections needed if any.

• The first section of the below relates to the 1996 and forward Bosch Motronic DME OBD-II equipped cars. These codes can be read by a generic code reader. 

• The later sections list codes for the other Porsche-specific modules in the vehicle requiring an advanced reader to access 
• Concluding with a section on OBD-I and earlier versions of BOSCH On-Board Diagnostic (OBD) engine management Diagnostic Trouble Codes (DTC) codes.

Related pages:

• Here is a document that describes diagnostic readers for use with the 993.

• Preparing for a State Emissions Test

• Dealing with a Secondary Air Injection (SAI) Emissions Fault

Table 1: DTC Versions, detailed desc. for the Master Code List, Table 3, Columns 3, 4, 5, & 6 

Version 1 Signal implausible / Implausible Component Section / Malfunction
Version 2 Interruption / No Signal = second column in list below
Version 3 Short to Ground / Below Lower Limit / Lean Mixture Limit
Version 4 Short to B+ / Above Upper Limit/ Rich Mixture Limi

Table 2: Malfunction Indicator Light (MIL),  sometimes refferd to as a check engine light, detailed descriptions for Master Code Table, Table 3 Column 7:

0 MIL is not triggered with this fault
1 MIL is on and Freeze Frame is stored in memory
2 MIL is on and a previous Freeze Frame is overridden
3 MIL is blinking and a previous Freeze Frame is overridden

Master Code Table 3: 993 Complete On-Board Diagnostic Code (OBDC) Listing

The first column in the below table is a listing of Diagnostic Trouble Codes (DTC) as reported to an OBD code reader. This reported code in combination with information in columns 3, 4, 5 & 6 described in Tables 1 & 2 above allows for the translation of the two or three-digit DTCs provided by your reader to the four-digit Bosch-Porsche "P" codes in columns three through six on the right providing detail information.

Below is a somewhat comprehensive list of Porsche Diagnostic Trouble Codes in addition to the above and for modules other than the engine-emission related ones listed above. It takes a 993 specific compatible scanner to access these codes:

[ABS5]
;Anti-lock/traction control trouble codes
11=Control unit faulty
12=Stop light switch
13=Incorrect gearwheel
14=Intake valve
15=Switch-over valve
17=Throttle (TP) information
21=Front left speed sensor, signal unplausible
22=Front right speed sensor, signal unplausible
23=Rear right speed sensor, signal unplausible
24=Rear left speed sensor, signal unplausible
25=Front left speed sensor open, short + or gnd
26=Front right speed sensor open, short + or gnd
27=Rear right speed sensor, open, short + or gnd
28=Rear left speed sensor, open, short + or gnd
31=Front left inlet ABS valve, open, short + or gnd
32=Front left inlet ABS valve, open, short + or gnd
33=Rear inlet ABS valve, open, short + or gnd
34=Rear left inlet valve, open, short + or gnd
35=ABS valve Exhaust FL, open, short + or gnd
36=ABS valve Exhaust FR, open, short + or gnd
37=ABS valve Exhaust RL, open, short + or gnd
38=ABS valve Exhaust RR, open, short + or gnd
39=Valve relay, open, short + or gnd
40=Return pump, open, short + or gnd



[H05]
;Climate control trouble codes
11=Inside temperature sensor
12=Left mixing chamber temperature sensor
13=Right mixing chamber temperature sensor
14=Evaporator temperature sensor
15=Rear fan temperature sensor
21=Oil cooler temperature sensor
22=Defrost flap motor
23=Footwell flap motor
24=Fresh air flap motor
31=Left mixing flap motor
32=Right mixing flap motor
33=Left heater blower motor
34=Right heater blower motor
41=Condenser blower motor
42=Oil cooler blower motor
43=Rear blower motor speed 1
46=Rear blower motor speed 1
44=Rear blower motor speed 2
45=Inside sensor blower motor
47=Rear blower motor speed 2


[H06]
;Climate control trouble codes
11=Inside temperature sensor
12=Left mixing chamber temperature sensor
13=Right mixing chamber temperature sensor
14=Evaporator temperature sensor
15=Rear fan temperature sensor
21=Oil cooler temperature sensor
22=Defrost flap motor
23=Footwell flap motor
24=Fresh air flap motor
31=Left mixing flap motor
32=Right mixing flap motor
33=Left heater blower motor
34=Right heater blower motor
41=Condenser blower motor
42=Oil cooler blower motor
43=Rear blower motor speed 1
46=Rear blower motor speed 1
44=Rear blower motor speed 2
45=Inside sensor blower motor
47=Rear blower motor speed 2

[B02]
;Airbag trouble codes
2=Driver ignition circuit to + or 0 V
5=Passenger ignition circuit to + or 0 V
17=Battery voltage low
19=Airbag Warning Light to + or 0 V
73=Short circuit ignition pills
76=Control unit fault cannot be erased
77=Result message cannot be erased
1=Fault memory cannot be erased
6=Fault memory cannot be erased
7=Fault memory cannot be erased
12=Fault memory cannot be erased
13=Fault memory cannot be erased
14=Fault memory cannot be erased
15=Fault memory cannot be erased
16=Fault memory cannot be erased
18=Fault memory cannot be erased
23=Fault memory cannot be erased
48=Fault memory cannot be erased
49=Fault memory cannot be erased
50=Fault memory cannot be erased
51=Fault memory cannot be erased
52=Fault memory cannot be erased
53=Fault memory cannot be erased
54=Fault memory cannot be erased
55=Fault memory cannot be erased
56=Fault memory cannot be erased
57=Fault memory cannot be erased
58=Fault memory cannot be erased
59=Fault memory cannot be erased
60=Fault memory cannot be erased
61=Fault memory cannot be erased
62=Fault memory cannot be erased
63=Fault memory cannot be erased
65=Fault memory cannot be erased
67=Fault memory cannot be erased
68=Fault memory cannot be erased
69=Fault memory cannot be erased
70=Fault memory cannot be erased
71=Fault memory cannot be erased
72=Fault memory cannot be erased


[B03]
;Airbag trouble codes
04=Driver ignition circuit
05=Driver ignition circuit
10=Passenger ignition circuit
11=Passenger ignition circuit
03=Battery voltage low
01=Airbag Warning Light
02=Airbag Warning Light
73=Short circuit ignition pills
01=Fault memory cannot be erased
70=Child seat detection
71=Child seat detection
72=Child seat detection
100=Control unit faulty
20=Driver ignition circuit
21=Driver ignition circuit
36=Driver ignition circuit
26=Passenger ignition circuit
27=Passenger ignition circuit
39=Passenger ignition circuit
73=Child seat detection
100=Control unit faulty
101=Control unit faulty
102=Control unit faulty
103==Control unit faulty

[I00]
;Alarm System trouble codes
11=Control unit faulty
12=Voltage failure term 30, active alarm
13=Voltage failure term 30 during output
14=Position of drives unplausible
15=Door open during activation
16=Engine lid open during activation
17=Luggage lid open during activation
18=Glove box open during activation
19=Input 2 to gnd during activation
20=Central locking system button closed during activation
21=Input 1 to gnd during activation
22=Input 3 to positive during activation
23=Fault memory
24=Fault memory
25=Fault memory
26=Fault memory


[I01]
;Alarm System trouble codes
11=Control unit faulty
12=Voltage failure term 30, active alarm
13=Voltage failure term 30 during output
14=Position of drives unplausible
15=Door open during activation
16=Engine lid open during activation
17=Luggage lid open during activation
18=Glove box open during activation
19=Input 2 to gnd during activation
20=Central locking system button closed during activation
21=Input 1 to gnd during activation
22=Input 3 to positive during activation
23=Fault memory
24=Fault memory
25=Fault memory
26=Fault memory


[G00]
;Tiptronic trouble codes
11 – Signal Implausible
13 – Voltage for drive links failed
14 – Voltage for sensors failed
21 – RPM signal from DME failed
22 – Load signal from DME failed
23 – Throttle Pot. Failed
24 – Change of ignition timing
31 – Solenoid valve 1 failed
32 – Solenoid valve 2 failed
33 – Solenoid valve torque converter clutch failed
34 – Pressure regulator failed
35 – Selector lever switch/transmission failed
36 – Transmission speed sensor failed
37 – Transmission temp. sensor failed
38 – Selector lever switch/ transmission partial failure
42 – Transmission control unit failure
43 – Transmission control unit failure
44 – Transmission control unit failure
45 – Downshift fault in rev limiter
46 – Downshift fault in rev limiter
51 – Manual program switch failed
52 – Tip. Switch up and down failed
53 – Kick down switch failed
54 – Transverse accel. Sensor failed
55 – Speed signal 1 from ABS control unit failed
56 – Input to combination instrument failed
57 – Transmission oil cooler blower relay failed
59 – Switch R-position failed
60 – Reverse light relay failed

This link points to a listing of BOSCH ignition/induction systems used in the various models & engines of Porsche vehicles: related to the BOSCH Engine Management. versions listed below**:

**Here is a link to the original BOSCH document of all Makes/Models the above link is clipped from.

Below are listed the codes for OBD-I and other BOSCH engine management versions:

[M04]
;Motronic trouble codes
11=Power supply, DME, high
14=Engine temperature sensor 2
15=Throttle Potentiometer
16=Throttle Potentiometer
18=RPM Signal
19=Speed signal / Speedometer
21=Hot-wire mass air flow sensor
22=Oxygen sensor (Sensor signal)
23=Oxygen regulation / stop (intake air leak?)
24=Oxygen sensor short to+ or 0 Volts
25=Intake air temperature sensor
26=Ignition timing change
27=IAC opening/closing winding
28=IAC opening/closing winding
31=Knock sensor 1
32=Knock sensor 2
33= Control unit faulty, Knock computer
34=Hall signal
36=Idle CO potentiometer
41=Control unit faulty 
42=Fuel pump relay (DME relay)
43=Tank ventilation valve
44=Auxiliary air pump relay
45=Warning lamp Check Engine
51=Injection valve 1
52=Injection valve 2
53=Injection valve 3
54=Injection valve 4
55=Injection valve 5
56=Injection valve 6
67=Ignition final stage
68=Ignition final stage
69=Ignition final stage

[M06]
;Motronic trouble codes
11=Power supply, DME, high
14=Engine temperature sensor 2
15=Throttle Potentiometer
16=Throttle Potentiometer
18=RPM Signal
19=Speed signal / Speedometer
21=Hot-wire mass air flow sensor
22=Oxygen sensor (Sensor signal)
23=Oxygen regulation / stop (intake air leak?)
24=Oxygen sensor short to+ or 0 Volts
25=Intake air temperature sensor
26=Ignition timing change
27=IAC opening/closing winding
28=IAC opening/closing winding
31=Knock sensor 1
32=Knock sensor 2
33=Control unit faulty, Knock computer
34=Hall signal
36=Idle CO potentiometer
41=Control unit faulty 
42=Fuel pump relay (DME relay)
43=Tank ventilation valve
44=Auxiliary air pump relay
45=Warning lamp Check Engine
51=Injection valve 1
52=Injection valve 2
53=Injection valve 3
54=Injection valve 4
55=Injection valve 5
56=Injection valve 6
67=Ignition final stage
68=Ignition final stage
69=Ignition final stage

Here is a page of OBDC use notes

Preparing of a State Emissions Test

Dealing with a Secondary Air Injection (SAI) Emissions Fault

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