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Autopapyrus · Nissan Primera 2.0 TD CD20T (1998)
https://autopapyrus.com/guides/nissan/primera/ecm-computer-diagnostics/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Nissan Primera 2.0 TD CD20T (1998): ECM computer diagnostics

On the CD20T diesel, engine management is handled by the ECM of the ECCS-D system. It stores fault codes and shows them with the MI lamp in the instrument cluster. Codes can be read in two ways: by counting the lamp flashes or with a CONSULT scan tool. Generic OBD-II scanners often do not work on cars from these years, because they use their own connector and protocol.

DifficultyMedium Time30-60 minutes Steps13

Key figures

  • Wait time before erasing codes
    at least 5 seconds. After turning the key to LOCK, wait, then turn the ignition on again (step 12)
  • Pause between diagnostic mode switches when erasing codes
    at least 2 seconds. Switch from Mode II to Mode I twice without a scan tool (step 12)
  • Number of codes the ECM stores
    up to 7 with the highest priority in each group. After the repair, erase the codes and recheck to see the remaining ones (step 8)
  • Battery voltage
    12 V. Use only a 12-volt battery during diagnostics, and remove the negative terminal before disconnecting the ECM connector (steps 1 and 11)

Check these values against the manufacturer’s specification for your vehicle before you start.

Diagram: where the diagnostic connector and ECM are and how to find them

View from under the dash near the pedals1Diagnostic connector2Lower edge of the panel3PedalSeparate view: ECM unitThis is a different place, not under the dash5Blue connector and harness4ECM unitMetal bracket with holesTap to enlarge
  1. 1CONSULT diagnostic connector: a white block with two rows of sockets on a metal bracket. Connect the interface or the CHK and IGN jumper here.
  2. 2Lower edge of the panel: a landmark, the connector is visible below it.
  3. 3Pedal: a landmark at your feet, the connector is to the right.
  4. 4ECM unit: stores fault codes. Do not take it apart.
  5. 5Blue ECM connector with the wire harness: before unplugging, switch the ignition off and disconnect the negative battery terminal.

Parts

2
№Part
01 Engine management system sensorsif faulty, based on retrieved fault codes
02 Engine warning lamp (MI) bulb in the instrument clusterif faulty

Tools

5
  • scan tool with Nissan CONSULT support (or a CONSULT interface for a laptop)
  • jumper wire for connecting the CHK and IGN terminals
  • multimeter
  • wrench for removing the battery terminal
  • flashlight
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 2 more. See manuals →

Step by step

13 steps
  1. Check the conditions. The battery must be a healthy 12-volt unit and well charged. Switch the engine off and turn off all electrical loads.
  2. Find the CONSULT diagnostic connector. It is located inside the cabin, usually near the fuse box under the left side of the dash, sometimes behind a cover. On 1996-1998 cars the pinout may differ from the diagrams circulating online for gasoline models. For this reason, to connect a laptop, use an interface confirmed specifically for the CD20T diesel, and do not solder an adapter from someone else's diagram.
  3. Check the lamp. Turn the ignition on without starting the engine (Diagnostic Test Mode I). The MI lamp in the cluster should stay on continuously. If it does not light, first check the bulb itself and its circuit, otherwise you will not see the code flashes.
  4. Start the engine. If the MI lamp is on with the engine running, the ECM has detected a fault. If the lamp stays on or flashes erratically, drain the water from the fuel filter: there may be water in the fuel.
  5. Read the codes without a scan tool. Switch the engine off and turn the ignition on. Put the ECM into Diagnostic Test Mode II: connect the CHK and IGN terminals on the diagnostic connector with a suitable jumper wire. Check the exact connect and disconnect sequence against the manufacturer's service manual. Do not switch modes while the engine is running.
  6. Read the MI lamp flashes. A code is output as a series of flashes: long flashes give tens, short flashes give units. For example, 12 or 43. Write down all the codes in order.
  7. Decode the codes. The main ones for the CD20T: 12 - mass air flow sensor; 13 - engine coolant temperature sensor; 14 - vehicle speed sensor; 15 - control sleeve position sensor (injection pump); 18 - pump electric governor; 21 - injection timing control valve; 28 - cooling fan (overheating); 34 - needle lift sensor (injector); 36 - fuel cut solenoid valve; 42 - fuel temperature sensor; 43 - accelerator pedal position sensor and switch; 47 - crankshaft position sensor (TDC); 83 and 98 - glow plug system; 85 - A/C cut; 86 - EGR valve; 87 - brake light switch; 92 - ECCS-D relay; 97 - MI lamp and diagnostic circuit; 31, 82, 84, 91, 93 - the ECM itself.
  8. Be aware of the limitation of this method. Flash codes cannot tell a current fault from one that disappeared long ago. The ECM stores up to 7 highest-priority codes in each group, and a new code may push out a less important one. The CONSULT scan tool shows the fault name as text and separates current faults from past ones, so it is better to use it for accurate diagnosis.
  9. Diagnostics with a scan tool. Connect the interface, turn the ignition on, select ENGINE, then SELF-DIAG RESULTS. For live data, use the Data Monitor and Active Test modes to check sensors and actuators in operation.
  10. Check the wiring and connectors according to the code found. Inspect the sensor connector for corrosion, broken wires and chafed harness, and measure the supply voltage, ground and sensor resistance with a multimeter. Do not replace a sensor until the wiring has been ruled out.
  11. Before disconnecting the ECM connector, turn the ignition off and remove the negative battery terminal: battery voltage is supplied to the unit even with the ignition off. The tester probes must not touch each other when measuring at the unit, because a short circuit can damage the ECM power transistor. Do not disassemble the ECM, and do not disassemble the fuel pump, injector No. 1 with the needle lift sensor, or pump components that are not meant to be taken apart.
  12. Fix the fault and erase the codes. If the ignition was left on after the repair, turn the key to LOCK, wait at least 5 seconds, and turn the ignition on again without starting the engine. Without a scan tool, then switch the unit from Mode II to Mode I twice, leaving at least 2 seconds between switches. With a scan tool: ENGINE, SELF-DIAG RESULTS, ERASE. A code can be erased only if the ECM considers the fault to be fixed.
  13. Do a final check. Start the engine, warm it up and take a test drive. Make sure the MI lamp does not come on and the code has not returned. If the code appears again, look for the cause deeper: wiring, ground, power supply.

Common mistakes and warnings

  • Do not disconnect the battery terminals or pump connectors with the engine running, as this can damage the electronics
  • After the battery is disconnected, the ECM resets its learned values, and the engine may run slightly differently for a while
  • This is not a fault, and no parts need to be replaced because of it
  • Do not press the accelerator pedal when starting
  • Check the exact sensor resistance values, sensor tightening torques and the Mode II terminal-connection sequence against the manufacturer's service manual
  • If you have no experience with electrical work and the code points to the ECM or the fuel pump, take the car to a repair shop with diesel equipment