How to Read 1996 Peugeot 306, Pre-OBD2 Fault Codes. 2-pin PSA Connector.

Introduction

Prior to the introduction of mandatory OBD2 systems in Europe, which were introduced in the early 2000s (compared with 1996 for the USA). There were many differing methods of logging and retrieving onboard diagnostic and performance information depending on manufacturer and model of car.

Peugeot Citroen Group PSA used a 2-pin DLC connector for many of their models up until around 1997 and a 30-pin DLC connector until the early 2000's. All 2-pin DLCs allowed reading of 2 digit flash codes, whereas only some 30-pin DLCs allowed reading of 2 digit flash codes.

Flash codes give the operator a reading of the code by turning on and off voltage to a test device such as a lamp, oscilloscope or fault code reader. They are not very sophisticated and quite slow, however they can be read by anyone with very basic equipment and by taking basic precautions.

In this instructable I will show how to read the stored codes from a 1996 model, left-hand drive Peugeot 306. This car has a Bosch Motronic MP5.1 engine management computer and a 1.6 litre TU5 JP (NFZ) engine. This will be demonstrated using three methods. These methods are: fault code reader (specifically the Haynes PFCR), LED test lamp and oscilloscope.

The methods shown here will work for some other models of Citroen and Peugeot up until the introduction of OBD2. However certain details can vary and this information should be checked before proceeding. I have provided links at the end of this instructable to aid in information finding.

Accompanying video

Included with this page is a video demonstrating the process and some of the theory. By no means good quality, but should give what is needed to follow the process.

General warning

Be careful with automotive electronics, simple mistakes can lead to expensive repairs. I am not responsible for anyone bricking their engine management computer. Be careful and don't do anything if you don't fully understand what it is you're doing.

Step 1: Background Information on PSA Flash Fault Codes.

The fault codes given by Peugeot and Citroen cars with flash code generating engine computers are very simple to interpret and readable by rudimentary means.

The codes these cars generate are 2 digits long and manifest as a series of on and off pulses given through a green 2-pin data link connector (DLC) shown in the figures 1 & 2. On the specific car under test in this instructable this code also gets flashed through the check engine light, although this is not always the case. Some models have a 30-pin DLC, these models are not specifically covered in this instructable, although the code sequence is given in the same format.

When reading a sequence of codes there will always be at least two codes indicated. These are codes 12 and 11, in that order. If these codes appear alone then no actual fault codes have been logged. If actual fault codes have been logged they will appear between code 12 and 11.

In figure 3 is an example of how code 12 followed by 11 appears as an idealised voltage trace (this sequence indicates a start and end code, with no faults present). Figure 4 shows an example code 41 as an idealised voltage trace.

From these figures it is clear to see that the 2 digit codes manifest themselves as such:

1. The first digit comes as a flash (or series of flashes in quick succession)
2. This is followed by a pause of about 1.5 seconds
3. The second digit comes as a flash (or series of flashes in quick succession).

Codes are separated by at least 3 seconds.

In figure 5 it can be seen that (in the car under test) the DLC, engine management unit and check engine light are all connected to each other in the same circuit. As such, care must be taken when performing any tests.

1996 Peugeot 306 1.6 (NFZ) fault codes

For this model of engine and computer the following codes can be read:

Informational codes:

• 11: End of codes
  • This code always appears. Actual faults come before this code.
• 12: Beginning of codes
  • This code always appears. Actual faults come after this code.

Fault codes:

• 13: Intake air temperature sensor or circuit
• 14: Engine coolant temperature sensor or circuit
• 21: Throttle position sensor or circuit
• 22: Idle speed regulator
• 31: Oxygen sensor or circuit
• 33: Manifold absolute pressure sensor or circuit
• 41: Crankshaft position sensor or circuit
• 42: Injector or circuit
• 51: Oxygen sensor or circuit
• 52: Mixture control, supply voltage, air or exhaust leak
• 53: Battery voltage incorrect
• 54: ECM failure

A note on actuator tests

With some engine computers it is possible to induce a test of various actuators in the vehicle. This is done in a similar way to the fault code reading. They are not available on all models. Below is a list of actuators that potentially could be tested depending on model.

• 81 or 91: Fuel pump, relay and circuit
• 82 or 92: Injector and injector circuit
• 83 or 93: Idle speed control valve and circuit
• 84 or 94: Carbon filter solenoid and circuit
• 85 or 95: Air conditioning compressor, relay and circuit
• 86 or 96: Variable air intake and circuit (A)
• 87 or 97: Variable air intake and circuit (B)

Caveats

The most important caveat to any fault code reading is that the fault code (along with other more noticeable condition such as driveability, rough idle, lack of power, etc.) are just symptoms of a problem. Just because a MAP sensor code pops up doesn't mean the MAP sensor needs replacing, instead it makes sense to check the sensor, voltages, wiring, manifold itself, engine computer terminals (carefully) etc. before making any changes or replacing any parts.

A note about the DLC, there can be more 2-pin diagnostic connectors scattered around the engine bay, so be sure to use only the green one for these tests, some possible colours are listed below.

• Green: Engine
• Grey: ABS
• White: Airbag
• Brown: HVAC
• Black: Locking system

These connectors and their location are model dependent.

Step 2: How to Read Peugeot and Citroen 2-pin Fault Flash Codes. Using Haynes PFCR.

The Haynes PFCR (Professional fault code reader) was a consumer fault code reader for early onboard diagnostic featured cars, prior to the introduction of OBD2. The reader was introduced in the late 90s and a starter kit cost just over £400. An overview of all components for the specific car under test are shown in figure 1.

This device consists of a handheld unit with buttons and a screen (figure 2). In the back of this unit is a cartridge slot (figure 3 & 4) into which are inserted "pods" (figure 5 & 6) which contain the software to read the codes of various makes and models of car. There is also an 8-pin mini-DIN socket on the top of the unit (figures 7 & 8) into which plugs the desired cable for the model car under test.

Power is provided by the diagnostic port or battery crocodile cables (figure 1 shows all of these cables together and figures 9 & 10 show the PSA specific connector), depending on the model under test. Various views of the PFCR are shown in the figures.

Haynes pods

Each manufacturer had a pod that would be purchased separately (along with the correct cables and manual pages) which would fit into the PFCR to allow it to read codes for that particular manufacturer's vehicles. Along with manufacturer specific pods, there were available "MegaPods" with multiple manufacturer's software on them. Without a pod the device will not switch on.

The pods were all roughly the same with the software being included on a small chip inserted during manufacture (figure 11 shows the internals of a broken one). The pods contain all of the operating software with the device itself only used for processing, user input and displaying information.

Using the PFCR

These instructions are for the specific car under test. However, they are still fairly general, although please bear in mind different manufacturers, models and pods will have slight differences. Generally it is safe to follow the guidance given by the device and manual (if available).

1. Insert the correct Pod into the back of the PFCR.
2. Ensure the ignition is off.
3. Connect the test cable to the PFCR and to the DLC connector, remembering to connect the battery leads if necessary. Once power is received by the PFCR it will power on.
   • Figures 12 & 13 show the PFCR set up for reading the car featured in this instructable. This would change for other makes and models of course. Figure 14 shows a close up of the test plug inserted into the DLC.
4. Using the up (↖) and down (↘) arrows navigate through the Pod and software version information until reaching the make selection menu.
5. Press the tick mark (✓) once the desired manufacturer is selected.
6. Select "1. Standard" and press the tick mark (✓).
7. The PFCR now displays "Turn Ignition On". Turn the ignition on but do not start the engine. In this car there was a keypad immobiliser, the correct code must be entered before any codes can be read. Once this is done press the tick mark (✓).
8. Select "1. Read faults" and press the tick mark (✓).
9. Wait for the PFCR to read the faults. As this is a flash code only car there will be quite a wait, especially if there are many codes. The PFCR will display "Searching..." and tick as it does so. It will then show "Reading faults" and continue to tick.
10. The PFCR will then display "X Faults Found", press the tick mark (✓).
11. If there are faults then select "1. View Faults" and press the tick mark (✓).
    • If there are no faults press the (X) and then confirm the "Are you sure" by pressing the tick mark (✓).
    • Turn off the ignition and disconnect the PFCR.
12. Scroll through codes by using the left (↖) and right (↘) arrows.
13. Once finished with the codes press the (X) and if desired choose to clear them.
14. Press (X) and then confirm by pressing the tick mark (✓).
15. Turn off the ignition and disconnect the PFCR.

PSA cable connections

Figure 15 shows the general wiring arrangement of the PSA 2-pin connector for the Haynes PFCR.

Online manual

A full manual for the PFCR is available for download here. Including vehicle specific information. Bear in mind, this may have subtle differences depending on the age of your own unit and pods available.

Step 3: How to Read Peugeot and Citroen 2-pin Fault Flash Codes. Using a Test Lamp.

The test lamp (figure 1) is the most common and accessible method of performing this reading (other than viewing the check engine light, if available). Generally as the DLC diagnostic connector is linked directly to the engine computer, it is advisable to use an LED test light.

An overview of all the equipment needed is shown in figure 1, a schematic layout of the testing procedure is shown in the figure 2, a basic idea of how to construct an LED test lamp is shown in figure 3, the DLC connector with pin 2 numbered is shown in figure 4 and the set up for the specific car under test is shown in figure 5.

Code reading procedure

1. Ensure the ignition is off.
2. Connect test lamp (positive) to battery positive and connect test lamp (negative) to pin 2 of the green data link connector (DLC). Attach another wire to this same pin but don't allow it to ground just yet, a T pin or backprobe is useful here. The test lamp will probably illuminate at this stage.
3. Turn the ignition on but do not start the engine. In this car there was a keypad immobiliser, the correct code must be entered before any fault codes can be read.
4. Read each fault code in sequence, fault code sequences begin with code 12 and end with code 11. If these codes appear next to each other then there are no codes saved.
   1. Touch the free end of the grounding cable to the battery negative or other grounded location, do this for about 3 seconds, do not do it for longer than 10 seconds, as this will clear the codes.
   2. Once the ground is released the light should go off, and shortly after it should flash the first digit(s), if more than one, these flashes happen in quick succession.
   3. Once the first digit is flashed there will be a pause of about 1.5 seconds.
   4. The second digit(s) will now flash, if more than one, these flashes will happen in quick succession.
   5. Wait until the lamp comes back on (about 3 seconds) and repeat the process from point 1.
      • Once code 11 is read, the stored code sequence has finished and any further reading will start from the beginning.
5. Turn off the ignition and disconnect the test lamp.

Code clearing procedure

1. If any repairs or work have been carried out since the last check, perform a drive test and re-check for new fault codes following the above instructions.
2. If the code sequence is 12 followed by 11 there are no codes stored.
3. Short the end of the grounding cable to the battery negative or other grounded location, do this for over 10 seconds, this clears the codes.
4. Turn off the ignition and disconnect the test lamp.

It is also possible to clear the codes by disconnecting the battery for several minutes. This, however, deletes engine computer learned values and resets radio, clock and other equipment that relies on constant power.

Step 4: How to Read Peugeot and Citroen 2-pin Fault Flash Codes. Using an Oscilloscope.

Using an oscilloscope to read flash codes is a little overkill, however if you wished to keep a record of what was reported or you have one to hand it is simple to set up.

The test setup is essentially the same as for the test lamp (figure 1). Instead of the test lamp simply substitute the oscilloscope test lead.

A schematic layout of the testing procedure when using a test lamp is shown in the figure (), an overview of all the equipment needed is shown in figure (), the DLC connector with pins numbered is shown in figure () and the set up for the specific car under test is shown in figure (). The result of testing a vehicle with no codes is shown in figure ().

Code reading procedure

1. Ensure the ignition is off.
2. Ensure the oscilloscope is ready to receive the signal.
3. Connect the oscilloscope positive lead to battery positive and connect the ground lead to pin 2 of the green data link connector (DLC). Attach another wire to this same pin but don't allow it to ground just yet, a T pin or backprobe is useful here. The oscilloscope will probably show a signal at this stage.
4. Turn the ignition on but do not start the engine. In this car there was a keypad immobiliser, the correct code must be entered before any fault codes can be read.
5. Read each fault code in sequence, fault code sequences begin with code 12 and end with code 11. If these codes appear next to each other then there are no codes saved.
   1. Touch the free end of the grounding cable to the battery negative or other grounded location, do this for about 3 seconds, do not do it for longer than 10 seconds, as this will clear the codes.
   2. Once the ground is released the signal should drop off and shortly after it should log one of more peaks forming the first digit of the code, these peaks happen in quick succession.
   3. Once the first digit is logged there will be a pause of about 1.5 seconds.
   4. The second digit will now be logged, these peak(s) will happen in quick succession.
   5. Wait until the voltage comes back up and stays up (about 3 seconds) and repeat the process from point 1.
      • Once code 11 is read, the stored codes have finished and any further reading will start from the beginning.
6. Turn off the ignition and disconnect the test equipment.

Code clearing procedure

1. If any repairs or work have been carried out since the last check, perform a drive test and re-check for new fault codes following the above instructions.
2. If the code sequence is 12 followed by 11 there are no codes stored.
3. Short the end of the grounding cable to the battery negative or other grounded location, do this for over 10 seconds, this clears the codes.
4. Turn off the ignition and disconnect the test equipment.

It is also possible to clear the codes by disconnecting the battery for several minutes. This, however, deletes engine computer learned values and resets radio, clock and other equipment that relies on constant power.

Step 5: Additional Reading Methods and Links.

Additional methods of reading codes

Smartphone oscilloscope.

It is possible with modern smartphones to log codes using a home made cable and oscilloscope application. Two possible resources are linked below.

A very simple cable adaption to make a phone scope cable. There would be no need to have the switch and multiple resistances, just the resistance for 20V would suffice here.

Instructable to make a slightly more advanced phone scope cable.

Draper fault finder

Draper Tools in the past sold a fault finding device for specific vehicle manufacturers. Their Peugeot/Citroen (68079) model was simply a limited test lamp with a switch. It is plugged into pin 2 of the DLC and connected to the battery. The switch on the device is operated for 3 or so seconds and then the LED on the device flashes the fault codes as with the simple test lamp method.

PDF manual for the tool.

Check engine light

As mentioned before, many of these flash codes flash to the check engine light. So if the check engine light is functioning and your car is one which does this, there is no need for the test lamp, scope etc.. The PFCR is also a little overkill for these kinds of tests, however for more complicated pre-OBD systems they are very useful.

Further reading

Information on different Peugeot models' DLC diagnostic connectors.

Information on how to set up code reading of 2-pin DLCs.

PDF book of different manufacturer fault codes and directions for reading.

PDF of a Haynes book with manufacturer fault codes and diagnostic information.

A complete manual for the PFCR is available for download here. Including vehicle specific information. Bear in mind, this may have subtle differences depending on the age of your own unit and pods available.

Peugeot service box. This requires sign up but is the official service manual and technical site for Peugeot cars. Some information is free (parts manual), some requires payment (repair guides, wiring diagrams, etc.).

Internal circuit boards of the Haynes PFCR unit and pod.

Step 6: Thanks

Thanks for your attention and I hope this was useful for you. If you have any questions then please ask, I don't come here very often, but I will answer if I can when I can.

All the best and take care.