# checking codes



## 84720pickup (Oct 17, 2006)

how do i check codes on my 84 720 pickup? i have the 2.4L and the sensor light is on. i know that the temp sensor is bad because it says the engines almost cold when its actually hot. the engine is also dieseling when i shut it off after it heats up.


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## 84720pickup (Oct 17, 2006)

anybody? i want to know if any other sensors are bad.


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## dvdswanson (Nov 6, 2005)

when I had my 86 720 KC the sensor lite came on at every 60k for a service to be done. I think theres a sticky on how to check the older vehicle lites.


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## moparmd (May 8, 2006)

*95 720 KC*



dvdswanson said:


> when I had my 86 720 KC the sensor lite came on at every 60k for a service to be done. I think theres a sticky on how to check the older vehicle lites.


My 95 720 KC has 69,000 miles and the check light just started coming on any help with how to fix it.


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## 84720pickup (Oct 17, 2006)

I wish I knew. Im still trying to find how to read the codes.


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## 88pathoffroad (Jun 6, 2004)

There are no codes. The engine is carbed, not computer-controlled.


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## 84720pickup (Oct 17, 2006)

88pathoffroad said:


> There are no codes. The engine is carbed, not computer-controlled.


then how do i find out what sensor is bad since the light is on? there is a computer mounted under the seat and i have an electric fuel pump and an o2 sensor. why would there be an o2 sensor wired up to the computer if it wasnt computer controlled?


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## 88pathoffroad (Jun 6, 2004)

I've been known to be wrong before, perhaps I am now. I've never heard of/personally experienced a 720 with a computer is all. Do you have a Chilton's book for it?


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## 84720pickup (Oct 17, 2006)

no, not yet. im just so confused with it. i have a 92 K1500 blazer with a computer and tons of sensors and i understand everything on it but with this truck i am lost. i have never heard of a carbureted engine with an electric fuel pump, o2 sensor, and some kind of air flow sensor in a plate underneat the carburetor. i cant figure out how the computer even comes into play but a sensor is bad. well, the sensors are kinda cheap so maybe i will just replace all of them since they all appear very old.


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## Minnyman (Aug 12, 2006)

84720pickup said:


> how do i check codes on my 84 720 pickup? i have the 2.4L and the sensor light is on. i know that the temp sensor is bad because it says the engines almost cold when its actually hot. the engine is also dieseling when i shut it off after it heats up.


These are the codes from the Haynes manual for 80-95 nissan pick-ups.
not sure if they will help though.
They are the test mode 3 codes










Heres some more, not sure why there different.


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## 84720pickup (Oct 17, 2006)

thanks for that, how do i get to making the light blink the codes?


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## Minnyman (Aug 12, 2006)

84720pickup said:


> thanks for that, how do i get to making the light blink the codes?


Here ye go...

Mode III (Stored Codes Test)

READING DIAGNOSTIC CODES 
The Electronic Control Unit (ECU) monitors several engine sensors and actuators. If a problem occurs the information is stored in the ECU's memory for retrieval.
The codes are displayed by the green and red diodes on the ECU. When the codes are extracted they are interpreted by the number of times the diodes flash.
The red diode will flash "X" number of times, this will represent units of ten, then the green diode will flash "X" number of times, this will represent units of one.
For example, if the red diode flashes once and the green diode flashes twice this should be interpreted as code 12. The codes are displayed in numerical order starting with the lowest and ending with the highest.

EXTRACTING DIAGNOSTIC CODES 

1. Access the ECU from under the R.F. seat and position it for observing the diodes. 
2. If the engine does not run, turn the key on and proceed to step #4. 
3. Start the engine and warm it to operating temperature then idle.
4. Turn the diagnostic mode selector on the ECU fully clockwise until both diodes flash 3 times then turn the selector fully counterclockwise. The ECCS system is now in mode 3. 
5. If the diodes do not illuminate, refer to ECU MAIN POWER AND GROUND TEST. 
6. Observe the diodes and note the code(s) displayed. Note: Code 55 indicates all systems are OK












ERASING DIAGNOSTIC CODES 

1. Turn the ignition key on. 
2. Turn the diagnostic mode selector on the ECU fully clockwise until both diodes flash 4 times then turn the selector fully counterclockwise. The ECCS system is now in mode 4. 
3. Turn the ignition key off. This will return the ECCS system to mode #1 (normal operating mode). 
4. ECU memory is now erased.

All this stuff comes from ALLDATADIY.COM - Do It Yourself Automotive Diagnostic & Repair Information, which in turn comes from the FSM, not sure if its copyrighted. I should be able to post it as im paying for it, eh, who knows.


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## 84720pickup (Oct 17, 2006)

thats odd. my computer doesnt have a red light or the little deals to turn. all it has is a hole on the side with a green diode inside. heres some pics.


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## Minnyman (Aug 12, 2006)

After browsing the manual further, you might be screwed. 

It says in 1984 only the california models got the ECCS all others came in 1985.

It also says it can only be serviced at a nissan dealership. If you can get a FSM or find someone with one for that specific 1984 california model it should have the codes, if there are any, in it.


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## 84720pickup (Oct 17, 2006)

i was wrong about the 84 thing. after going through the vin number i found out it was an 85. i guess i still must be screwed because i dont see anything that allows me to recieve codes.


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