Consult Quick Reference

Using a Consult Interface like Nissan Datascan, Conzult, ECUTalk, etc is a great way to diagnose and solve running issues with the Z32. Because the Z32 relies on a myriad of sensors to control the engine, understanding what each of these sensors does (or rather, what they should do) is the key to utilizing consult to its fullest.

This article provides an overview on the sensors and inputs that can be read through Consult, and what to expect when reading them.

Numeric Readings

These deal with variable sensors which return numeric data.

RPM

Engine RPM. This should match what the tachometer of the dashboard is reading. It's normal for the number to jump around in the same general area, or to display a few hundred RPM different from the tachometer. In this case, the tach is usually slightly inaccurate.
The RPM is read from the Crank Angle Sensor. It's normal for the RPM to "wiggle" a bit, but excessively jumpy RPM readings could indicate a poor connection to the CAS or a worn CAS drive pin. This will usually also manifest itself with "sloppy" idling and/or detonation under high boost.

Speed

Vehicle speed. Should closely match the speedometer on the dash. Note that if your speedometer is dead and Consult displays your speed at 0, that doesn't necessarily mean the speed sensor on the transmission is to blame. The speedometer itself has an internal speed sensor which transforms the transmission's sensor into a numeric figure. If the speedometer goes bad, a lot of times it prevents the ECU from reading the speed, as well.

Water Temperature

This is the water temperature as read by the ECU coolant temp sensor on the upper coolant pipe. While the gauge only displays a vague hint of the temperature, the ECU sensor is quite accurate.
This should be around ambient (outside air) temp on cold startup and should climb to 174°F to 190°F when fully warmed up. Excessively high temperatures indicate a problem with the cooling system.

AAC Valve

The AAC (auxiliary air controller) is the main valve that controls idle speed under normal conditions when the car is fully warmed up. The displayed number is a duty cycle that reflects the amount of time the valve is open vs closed. The valve rapidly opens and closes to let in a variable amount of air, so a duty cycle of 35% would effectively mean the AAC is 35% open.
This number fluctuates depending on multiple conditions (like the condition of the engine, the ambient temperature, etc). But generally, when warm, the duty cycle is around 30%. If the number is 15% or lower, this often means a vacuum leak is present, as 15% is the lower threshold of the AACs operation, and this indicates the ECU attempting to lower the idle speed. Excessively high duty cycle indicates that the base idle screw on the IACV is too far closed, and is causing the AAC to open more than it should half to in order to prevent stalling.

Ignition Timing

This is the current ignition timing. The ECU changes the timing rapidly and constantly depending on various conditions, like engine RPM, load, and temperature.
At warm, normal idle, the timing should be at 15 degrees BTDC (and a timing light check should reflect that, indicating the CAS is correctly positioned).
It should be noted that this value indicates what the ECU is attempting to fire at. The CAS must be adjusted properly so that the ECU's expected timing matches what's actually happening. Many users read 15 degrees from consult and assume their timing is correct, but this must be checked against a timing light.
At idle, the ignition timing should be at 15 degrees under normal conditions.
If the timing is sitting at 20 degrees at idle, this usually indicates that the Throttle Position Sensor is incorrectly set.
If the timing is sitting at 25 degrees at idle, this usually indicates that the neutral switch is turned OFF with an ECU for an automatic transmission.
Check out the ignition timing article for a bit more about how timing on the Z32 works.

Air Flow

This is the air flow as read by the MAF sensor, ranging between 0v (no airflow) and 5v (about 800 CFMs). It should follow the throttle position quite closely (in pattern, not in voltage). Shakey air flow readings usually indicate a vacuum leak.

Air Fuel Base

This is the "baseline" against which the ECU attempts to modify the air/fuel ratio, if at all. This is the portion of the tune that is "learned" through running. A neutral air/fuel base is 100. If the ECU receives a consistently lean or rich condition on one cylinder bank, it will tweak the base (usually not more than 1-3 units, but sometimes as high as 15) to compensate. Clearing the "self-learn" resets this to 100.

Injector Duty Cycle

Injector Duty Cycle is just that--the duty cycle of the fuel injectors. Fuel injectors cannot open partially, they are either fully open or fully closed. In order to inject different amounts of fuel, the ECU changes the duration of time for which the injector is open. 0% being closed at all times, and 100% being opened at all times. Fun fact, this percentage is directly proportionate to the flow rate of the injector. For example, 100% duty cycle of a 370CC injector indicates that the injector is flowing 370cc/minute of fuel. 50% duty cycle would indicate 185cc/min.

Injector duty cycle will fluctuate depending on the RPM and load of the engine, along with some other factors. It should be under 10% at idle, and you generally don't want it to exceed ~85% under high load/RPM.

O2/Oxygen Sensor

The Z32 uses two narrow-band oxygen sensors. These generate a voltage, between 0V and 1V, based on the amount of oxygen present in the exhaust gas. 0.5V would indicate the O2 is seeing a perfect stoichiometric air/fuel mixture. However, because oxygen sensors read after the combustion, it will never be right on. Instead, the ECU is constantly "bending" the air/fuel ratio based on input from the O2 sensors. Like balancing a broom on the palm of your hand, the reading from O2 sensors should constantly bounce between rich and lean. A bad O2 sensor will not respond much/at all (though this could also indicate an extremely rich or lean running condition).
It should be noted that O2 sensors are only utilized by the ECU when the engine is fully warmed up. Under normal, warm operating conditions, O2 sensors are often dormant at idle (though it's not unusual for them to flutter at idle). They should be tested by running the engine, fully warmed up, at 2000 RPM for at least one full minute. A healthy O2 sensor will fluctuate between lean and rich at least 5 times every 10 seconds. Under heavy load, the ECU richens the air/fuel ratio for safety, and you should see them peg towards the rich (<0.5V) side. Upon in-gear deceleration, the ECU reduces the amount of fuel injected, and you should see them peg towards the lean (>0.5V) side.

Battery Voltage

Guess. Just guess.
This it the output voltage read across the battery. With the car off, this should be around 12V. When running, it should be above 12V, generally around 13V or 14V. Voltage under 12V while running indicates a problem with the charging system (ie, the alternator).

Throttle Position Sensor

This is the variable numeric position of the throttle position sensor. The ECU sends 5V to the TPS, which reduces the voltage by a variable amount depending on the throttle position, then sends the new voltage back to the ECU. This is transmitted through the gray oval connector pigtail at the TPS.

At idle, with the throttle closed, this value should be between 0.4V and 0.5V. Higher or lower means the TPS needs to be adjusted. At wide open throttle (shut the engine off, please), the voltage should be between 4V and 5V. This value should smoothly increase as the throttle is opened.

See also the Hard Idle Switch information in the "switches and indicators" section below.

Fuel Temperature

This is the temperature reading provided by the fuel temp sensor, which is mounted to the fuel rail between cylinders 2 and 4 (front two on the US driver's side). The ECU uses this to enable or disable the PRVR solenoid. When this (or the solenoid) goes bad, the car often becomes hard to start when warm. This temperature shouldn't be too far from the water temperature.

Switches and Indicators

These are bi-polar (On or Off, True or False, etc) indicators.

Hard Idle Switch (Idle, Closed Throttle Position, etc)

The Hard Idle Switch is a switch built into the TPS that turns on when the throttle is fully closed, and turns off when the throttle begins to open. It is transmitted through the square connector on the front of the TPS.
If the switch is off when the car is idling with the throttle closed, this means the TPS is incorrectly set or is faulty. When setting the TPS at idle, the Hard Idle Switch should be ON while the Throttle Position Sensor is between 0.4V and 0.5V. There is a sweet spot when both of these become true. If you can't make this happen, usually the TPS is faulty.
If the Throttle Position Sensor is correctly set, but the Hard Idle Switch isn't, the car will tend to idle around 1500 RPM.

Power Steering

When the steering wheel is centered in the straight-ahead position, this switch should be off. When the steering wheel is moved, the power steering switch turns on to open the solenoid on the steering rack and provide power assist. The idle also raises slightly to compensate for this. If this is always on or always off, it could indicate a fault with the sensor on the steering rack (near the U-joint) or the clock spring behind the steering wheel.

Air Con Switch

When you turn the air conditioning on, this should turn on. This is displayed separately from the Air Con Relay because the climate control unit will turn the A/C Compressor off under certain conditions, even when the switch is on.

Air Con Relay

The A/C compressor relay may turn on or off under certain conditions, even if the air conditioning has been switch on by the user. When this happens, the Air Con Switch will show as ON, but the Air Con Relay will show OFF. If both are on (or even just the relay, if you've done a hack job), the compressor will be receiving power, assuming it's connected.

• R12 (90-93) models with manual climate control and all R134A (94+) models use a thermostatic sensor on evaporator to disable the A/C Compressor should the evaporator levels drop below a safe temperature. It re-enables the compressor once the temperature climbs.
• All models disable the A/C compressor when the refrigerant level is too low, as indicated by the sensor on the receiver/drier.
• R134A (94+) models disable the A/C compressor when the refrigerant pressure is too high or low, as indicated by the sensor on the receiver/drier.

Start Signal

This is the signal sent by the ignition switch when you crank the car over. The ECU plays with the fuel system slightly (running the fuel pump at battery voltage, for example) and the starter is engaged. This should only appear on when cranking the car.

Neutral

The transmission features a neutral switch indicating whether or not the car is in gear. The ECU tweaks the timing/fuel maps slightly depending on the position of this switch. On automatic cars, the timing is raised to 25 degrees BTDC when the car is taken out of neutral.

Fuel Pump

Indicates whether or not power is being supplied to the fuel pump. This will turn off if the ECU doesn't receive the 1 degree signal from the CAS (ie, the CAS isn't rotating or is not connected) and the car will stall.

Thermo/Aux Fan

Indicates whether or not the cooling fan is running. See the cooling fan article for conditions under which the fan operates. If it's running all the time, it usually indicates either a disconnected coolant temp sensor, or a bad ECU.

VTC

The VTC solenoids allow oil pressure to enter the VTC gears. The ECU will turn these on or off depending on the running conditions. They should generally be OFF while the engine is idling, and turn on under medium to heavy load. Most consult applications will allow you to manually enable or disable the VTC to see if it's working or not.

Waste Gate Solenoids

On turbocharged models, there are wastegate solenoids as a form of simple boost control. Under normal conditions, the solenoids are off and the car is able to achieve ~9.5 PSI of boost. When the solenoids receive power, the allow more vacuum to flow to the wastegate actuators, lowering boost to ~7 PSI.
The safety mode will be activated if the ECU is detecting detonation or has no connection to the detonation sensor (which throws Code 34).

Air/Fuel Ratio

This is a Rich/Lean indicator that displays reaction from the O2 sensors. Under 0.5V will display a rich condition, and over 0.5V will display a lean condition. See the "O2 Sensor" section above for more information about what to expect here.

EGR Solenoid

The EGR solenoid turns on at idle to provide vacuum signal to the EGR valve, allowing exhaust gas to enter the intake manifold and reduce emissions. Under normal operation, it should turn ON at idle and OFF off-idle.