QuestionCar is 1991 model with about 130,000km on the clock.
Often the ECM light will illuminate - sometime steady, sometimes blinking. Other times/trips it does not light up at all.
When it does light up, it is generally under light acceleration, such as going up a slight incline. It will blink while maintaining speed on a flat surface, but go off after backing off on the accelerator.
When starting car from cold, the ECM light generally does not illuminate - it is more likely to illuminate after starting the car whilst the engine is still warm.
Another issue is the automatic transmission kicking down unexpectedly - this usually (or only) occurs whilst cruising / maintaining speed, whether it be 60kmph or 100kmph, the behaviour is similar. The transmission will drop a gear, and in some instances two, causing the engine to dramatically rev up, particularly at 100kmph. To get the transmission to revert to the correct gear, I either back-off on the accelerator al together, or slightly depress the accelerator.
1. What is the ECM light? What can I do to fix the problem?
2. What is causing the transmission drop-down?
AnswerJohn,
You need to check the codes for the ECM and here is how it is done:
The ECU has a window on one side to view a red LED and a green LED - when checking fault codes, a red flash is worth 10, and a green flash is worth 1. So for example, the code to say that everything is functioning normally would be 5 red flashes and 5 green flashes - the code is 55.
The ECU has 5 modes of operation, for diagnostics codes, it has to be set to mode 3.
1. Make sure the screw next to the viewing window is turned clockwise.
2. Turn the ignition on
3. Both LEDs with flash once, then a pause, then a second time, then a pause, etc. etc. up to 5 times then will repeat the process. After is has flashed 3 times then turn the screw completely anti-clockwise. - this will select mode 3.
4. The LEDs will now flash codes. 55 means that everything is normal. The rest are written below.
5. When finished, turn the screw back to clockwise and the ECU will reset itself automatically.
Don't worry about the '5th cylinder misfire' and '6th cylinder misfire' or anything, the codes are the same for all Nissans.
11 Crank Angle Sensor/Camshaft Position Sensor.
12 Air Flow Meter/Mass Air Flow Sensor.
13 Engine Coolant Temperature Sensor.
14 Vehicle Speed Sensor.
21 Ignition Signal.
22 Fuel Pump.
23 Idle Switch.
24 Throttle Valve Switch.
25 Idle Speed Control Valve.
28 Cooling Fan Circuit.
31 ECM.
32 EGR Function.
33 Heated Oxygen Sensor.
34 Knock Sensor.
35 Exhaust Gas Temperature Sensor.
36 EGR Control-Back Pressure Transducer.
37 Knock Sensor.
38 Right hand bank Closed Loop (B2).
41 Intake Air Temperature Sensor.
42 Fuel Temperature Sensor.
43 Throttle Position Sensor.
45 Injector Leak.
47 Crankshaft Position Sensor.
51 Injector Circuit.
53 Oxygen Sensor.
54 A/T Control.
55 No Malfunction.
63 No. 6 Cylinder Misfire.
64 No. 5 Cylinder Misfire.
65 No. 4 Cylinder Misfire.
66 No. 3 Cylinder Misfire.
67 No. 2 Cylinder Misfire.
68 No. 1 Cylinder Misfire.
71 Random Misfire.
72 TWC Function right hand bank.
73 TWC Function right hand bank.
76 Fuel Injection System Function right hand bank.
77 Rear Heated Oxygen Sensor Circuit.
82 Crankshaft Position Sensor.
84 A/T Diagnosis Communication Line.
85 VTC Solenoid Valve Circuit.
86 Fuel Injection System Function right hand bank.
87 Canister Control Solenoid Valve Circuit.
91 Front Heated Oxygen Sensor Heater Circuit right hand bank.
94 TCC Solenoid Valve.
95 Crankshaft Position Sensor.
98 Engine Coolant Temperature Sensor.
101 Front Heated Oxygen Sensor Heater Circuit right hand bank.
103 Park/Neutral Position Switch Circuit.
105 EGR and EGR Canister Control Solenoid Valve Circuit.
108 Canister Purge Control Valve Circuit
The downshifting is probably due to the throttle kickdown cable being out of adjustment or the vacuum switch for the overdrive/lockup torque converter being worn or the vacuum hose to it being cracked or loose.
