QuestionHi, I have a 1987 Nissan Maxima, one problem is I can't get the idle down to specs (700-750 rpm), it will hover around 900-1000 rpm's.
2nd problem is a Failed smog test: Mechanic stated the vacuum signal is not getting to EGR valve. He also stated ECM is not breaking ground circuit or ground line is shorted to ground. Further investigation into why ground circuit is not being broken is necessary. What does this mean? What can I do? where do I start?
Thanks, Gary
AnswerGary,
The high idle is caused by a vacuum leak. Check all the vacuum lines for cracks or if one has come off. Second, check the line to the EGR valve and replace it. The EGR probably needs replacement too. The ECM uses grounds to control systems like injectors and the like. If a micro-relay on the mother board has failed you would get a code. You need to verify this after you correct the vacuum leak problem and the EGR problem. Once these are corrected, disconnect the battery and wait five minutes to reconnect it. The codes will be cleared. Now, drive the car at least three times to get the computer to go into normal mode of operations. If there is a problem it will reappear. If not you will pass SMOG. To read the codes on your car do the following:
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
