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12 - Fault Codes ( )


12.11 - Fuel Fail 11, idle trip signal out of range ( Brett Gadzinsky,  )

Fuel fail 11 is for the idle trip signal out of range. It has nothing to do with the throttle or the throttle position sensor.

The idle trim signal is built into the MAF (Mass Air Flow sensor). It is used to set the base idle mixture before oxy sensor correction. Normal output signal is about 2.5 volts and does not vary. Its set at the factory, and never needs adjustment.

It was used up to 1993 year cars, then Jaguar used an adaptive system.

The actual adjustment pot is built in the maf sensor, but is not really part of it, that's just where Jaguar (or bosch) stuck it. Since you cant get at it, its behind a sealed plug, it cant really go wrong, and your problem is likely from a dirty connection on the maf sensor.

The maf sensor is critical on how the engine runs, and its connections are sometimes abused by the connector hitting the coolant tank, make sure the connector is clean and tight. The first step would be to clean the connector using contact cleaner or WD40 , and then add a dab of dielectric grease to the contacts before reassembling. The parts stores sell the grease. You may have to disconnect the battery or pull the ECU fuse to clear the code.

If this doesn't fix it, the throttle pot itself may have failed. Cleaning the throttle body with solvent and getting it in the throttle pot can cause it to fail. The check procedure is nicely described in Haynes.


12.12 - Fuel Fail 12 : Mass Air Flow sensor out of range ( Brett Gadzinsky,  )



Output below .2 volts or above 4.5 volts engine rpm 400 to 3000 rpm for 5 crankshaft revolutions.

If FF 12 is flagged, ecu uses throttle position sensor input for engine load indications instead of the maf sensor.

Possible faults :

- Old style unsealed relays for EMS main 1993 year cars and up.
- Open or short in wiring between maf and main ecu.
- High resistance connection between maf and ecu (dirty connector at maf sensor).
- Open circuit in wiring from main relay power (12 volts) to maf.
- Bad maf sensor.

The maf sensor is in the air intake tract, after the air filter and before the throttle. It uses air flow through a side port to cool and change the resistance of sensors, corrected for ambient air temps to measure the air flow through the intake tract. Since it has no moving parts, its reliable, but suffers from having its connector in a bad spot. Its also subject to contamination of the sensors by any type of liquid.

Inside the sensor is a circuit board with voltage regulators, and a lot of parts and IC chips. On the 1988 to 1992 year cars, the base idle mixture trim is built in, but not part of the actual maf circuitry. Sensors to 1991 had a separate ground wire to a stud on the maf.

To test the maf, warm the car up to operating temps. At idle in park (about 740rpm) the output signal should read 1.2 to 1.5 volts, the higher the reading, the higher the indicated air flow. If your maf sensor puts out about 1.2 volts at idle, it is indicating a low air flow, so will adjust the injector pulse time down
to keep the mixture in range. 1.2 volts is on the low side of a normal reading and may cause problems unless you are at a high altitude.

If you have a vacuum leak, the INDICATED air flow into the engine will be low, the ecu will reduce the injector pulse, and you will have a lean mixture and a poor idle.

To test the high air flow, measure the output voltage with the car in drive, full throttle, foot on brake. Only do this test for a very short time, and use great care the car does not get away from you. At full throttle the maf should read about 3.0 to 3.3 volts. This is the torque converter stall reading, actual full throttle high rpm will indicate higher.

The maf sensor has a lot of input on the mixture and indicated load range the engine is operating at. A small change in the signal denotes a large change in mixture.

Under normal operating conditions, the maf sensor and the coolant temp sensor set the mixture and the way the engine runs.


12.14 - Fuel Fail 14 : coolant temp sensor out of range ( Brett Gadzinsky,  )



Conditions for flagging :

After cold start, signal to ecu under 3.53 volts after 6 minutes.
Normal engine operating temp, Signal decrease of .7 volts or greater in 196 milliseconds.
Normal coolant temp sensor out of operating range, Under .1 volt, above 4.9 volts for 64 milliseconds or longer.

If FF14 is flagged, the ecu defaults to 80F.

Possible faults:

- High resistance connection between the sensor and the ecu (dirty connection at coolant temp sensor)
- Open or short circuit in wiring between coolant temp sensor and ecu.
- High resistance ground circuit in ecu circuit.
- Defective engine thermostat.
- Defective coolant temp sensor.

The coolant temp sensor has 2 wires, and is located close to the engine thermostat. They very rarely fail.

The coolant temp sensor is used to control a number of functions:

- Cranking enrichment,
- Warm up enrichment,
- Acceleration enrichment,
- Air injection,
- Idle speed control,
- Exhaust gas recirculation,
- Evap system canister purge.

To test the coolant temp sensor, measure the resistance between the two terminals hot and cold.

14F 9200 ohms
32F 5900 ohms
50F 3700 ohms
68F 2500 ohms
86F 1700 ohms
104F 1180 ohms
122F 840 ohms
140F 600 ohms
158F 435 ohms
176F 325 ohms
193F 250 ohms
212F 190 ohms



12.16 - Fuel Fail 16 : intake air temp sensor out of range ( Brett Gadzinsky,  )


Conditions for flagging : signal to ECM under .1 or over 4.9 volts for 69 milliseconds. Default setting 86F if FF 16 is flagged.

Possible faults :

Dirty connection at air temp sensor,
High resistance or short between air temp sensor and ecu,
Bad intake air temp sensor.

The intake air temp sensors function is to retard the ignition timing during intake air temp rise to prevent detonation. The intake air temp sensor resistance reads he same as the coolant temp sensor.

14F 9200 ohms
32F 5900 ohms
50F 3700 ohms
68F 2500 ohms
86F 1700 ohms
104F 1180 ohms
122F 840 ohms
140F 600 ohms
158F 435 ohms
176F 325 ohms
193F 250 ohms
212F 190 ohms

At high engine loads, the air intake temp sensor retards the timing 2.25 degrees every 10C above 86F (30C), at light loads, it retards the timing starting at a higher temperature. It has NO effect on mixture.

The intake air temp sensor is located on the top of the elbow.


12.17 - Fuel Fail 17 : TPS out of range low ( Brett Gadzinsky,  )


Conditions for flagging : signal to ecu under 250 millivolts for 64 milliseconds.

The throttle position sensor is used by the ecu for :

- Idle speed control,
- Ignition idle strategy selection,
- Overrun fuel cutoff,
- Idle fuel trim (1990 to 1992)
- Main fuel metering strategy,
- Main ignition strategy,
- Acceleration strategy,
- Deceleration leaning,
- Full load enrichment.

Default settings while FF17 is flagged is 1.5 volts, and all throttle position sensor functions do not operate.

Possible faults :

- High resistance at throttle position sensor or ECM,
- Short or open circuit in wire harness between tps and ecu,
- Loose or incorrectly adjusted throttle position sensor,
- Defective throttle position sensor (worn).

On the 1990 to 1992 year cars, the tps has two separate sensors in one housing, one does the engine, the other does the transmission. After 1992, one sensor talks to both the engine and trans. On the early cars, to about 1993, the sensor is under the throttle and is turned by the throttle shaft.

Various year cars had different idle voltage settings :

87-88 .24 - .40
89-90 .31 - .36
90 and up .57 - .62

Full throttle should read about 4.5 volts.

Be careful to prevent anything getting in the tps while cleaning the throttle out...don't spray any cleaners in the throttle or the gunk will wash into the sensor.


12.18 - Fuel Fail 18 : TPSensor and MAF Sensor ( Brett Gadzinsky,  )



High throttle position signal, low air flow signal : the ECU looks for a combination of high throttle signal and low air flow signal that can not occur in a normally operating system.

Conditions for flagging :

- Throttle position sensor 2.25 volts or greater,
- Engine load site 3 or lower (low maf sensor output)

Response time : 5 engine revolutions.

Default settings: ignore throttle position sensor.

Possible faults:

- High resistance connection to ECU or throttle position sensor,
- Restricted air intake,
- Restricted exhaust,
- Low fuel pressure (low engine power)
- Ignition fault (low engine power)
- Engine mechanical fault,
- Short or open circuit between ECU and maf sensor,
- Incorrectly adjusted throttle position sensor,
- Bad throttle position sensor,
- bad maf sensor.

Check tps output signal, maf sensor output signal, engine vacuum readings.


12.19 - Fuel Fail 19 : Low Throttle Position Sensor ( Brett Gadzinsky,  )

High air flow signal, the ECM sees a combination of closed throttle and high intake airflow signals.

Conditions for flagging FF19:

- Throttle position sensor at idle,
- Engine load site 13 or higher,
- Engine rpm,s 1000 or higher for 5 or more crankshaft revolutions.

Default with FF19 flagged: ecu ignores throttle sensor and sets 1.5 volts, idle functions are disabled.

Possible faults:

- High resistance connection to ecu, maf sensor or throttle position sensor.
- Water in MAF sensor,
- Short or open in maf and throttle sensor wiring,
- Bad throttle position sensor.

Clean and wd40 the connections to the tps and maf sensors. Measure the throttle position sensor resistance at idle and as you open the throttle.


12.22 - Fuel Fail 22 fuel pump control circuit ( Brett Gadzinsky,  )



ECU flags FF22 if the signal to the fuel pump relay indicates open or shorted.

Conditions for flagging FF22:

- Ignition on,
- Fuel pump operating,
- indications of open or shorted fuel pump relay coil circuit.
- Response time 600 milliseconds

Possible faults:

- Low battery voltage,
- Poor ecu power feed or ground connections,
- Short or open circuit between ecu and fuel pump relay,
- Short or open circuit to oxy sensor heater relay (1993 and up),
- Loose connector pins (li18) 6 way PM4 yellow connector under air cleaner (1991-1992)
- Bad relay,
- Air pump relay circuit fault.

If the fuel pump does not work, but FF22 is NOT flagged, its the relay (contacts), the connections at the fuel pump, or a bad fuel pump.


12.26 - Fuel Fail 26 oxy sensor feedback lean ( Brett Gadzinsky,  )


Fuel fail 26 is . As the engine gets partly warmed up, it stumbles and sets the code. The code will clear when the trouble does, on the next restart.

Possible faults for a FF26 are :

- Low fuel pressure (plugged filter, weak pressure regulator on fuel rail, plugged system)
- Intake manifold air leak (vacuum hoses, intake manifold gasket, evap system hose rot, egr pipe rusted out, problem with air injection system (leaking valve).
- Ignition misfire, (bad plug, wires, cap, rotor)
- Purge valve stuck open (vacuum leak in evap system)
- Oxy sensor fault (not common)
- Bad maf sensor or connections.

Best to start with the ignition system : If the wires, cap, rotor are old, replace them, along with spark plugs.

The catalytic converters may eventually melt plugging the exhaust if the car is ran with the FF alarm on, so don't ignore it just because the engine runs ok.


12.3 - Code 3, Coolant temperature sensor. ( )


Code 3 says Coolant temperature sensor.

On the 1990 the codes are different. However, on my car there are two coolant temperature sensors located almost next to each other on the thermostat housing (top front of engine).

One drives dashboard temperature gauge via dash board computer. Other is used by ECU. The latter is the problem. You can find out which is which by disconnecting each and seeing if temperature gauge goes wacky (warm engine required).

Dashboard gauge sensor has just a single wire and other has connector. If the connections look OK (e.g. remove and clean). You can measure resistance with meter. Do when engine is cold and hot. At 25C (hot day-cold engine) it should be about 2500 Ohms. Hot engine (80C) about 300 Ohms


12.39 - Fuel Fail 39, EGR temp sensor circuit ( Brett Gadzinsky,  )


The ECM looks for a low egr temp signal when the egr valve is closed, and a high temp signal when the egr valve is open. The ECM also looks for an over temp signal when the egr system is enabled.

The egr temp sensor is located behind the throttle in the bottom of the intake manifold, close to the exhaust gas entry point.

The egr temp sensor is a negative temp coefficient thermistor :
Resistance decreases with temp increase.
Resistance, 122f 560,000 to 710,000 ohms.
Resistance, 212F 76,000 to 94,000 ohms.

Conditions for flagging FF39 :

- Engine coolant temp above 180F,
- Throttle position within expected range for engine speed,
- Engine speed 1700 to 3000 rpm,s,
- Load site range 2 to 7,
- Egr enabled, indicated temp greater than 525F for 64 milliseconds,
- EGR enabled, indicated temp under 212F for 60 seconds,
- EGR disabled, indicated temp greater than 122F for 5 minutes.

Possible faults:

- Blockage in EGR transfer pipe between egr valve and intake manifold,
- Blockage in intake manifold EGR adaptor port (90% of problems),
- Disconnected, leaking, blocked, pinched vacuum hose between,
- EGR valve and the egr vacuum solenoid,
- Defective EGR solenoid valve (stuck),
- Defective EGR valve,
- Defective egr temp sensor,
- Open or short in egr temp sensor wiring.

Most modern cars use exhaust gas into the intake tract to reduce combustion temps and NOx because exhaust gas is inert. It has no fuel or oxygen.

The EGR system ONLY operates when the engine is up to temperature and the engine is under light or moderate loads.


12.44 - Code 44 ( )


The code 44 and 26 have some overlap. Code 44 means that the oxygen sensor is signaling the computer that the fuel mixture is bad - too rich or too lean. The car can then not run in closed loop mode, and the VCM after a while ignores the oxygen sensor and goes to a default mode. If the sensor itself was bad, the car would probably run just fine, but use more gas, although in some cases will run irregularly. More likely you have a true, too lean or too rich problem.

The first step in diagnosis is to idle the car until the car runs rough or the error light is activated. Then, using a DIGITAL multimeter, measure the output of the oxygen sensor by back probing it while still connected - do this at the junction of the wire from the sensor on the right (US) fender well. It will oscillate rapidly under normal conditions from .9 to 2v. If mixture is too lean it will read very low all the time. Check with a manual for the actual voltages, these may be incorrect, or vary between models.

TOO LEAN: If you determine that the mixture is too lean, then you have either fuel starvation or an intake air leak. If the car idles OK but has loss of power at speed, then you likely have fuel starvation. An intake air leak will cause bad idle but will be less noticeable at speed.

TOO RICH OR AMBIGUOUS: This could be a sensor problem (air mass sensor, throttle pot or others), but most likely an ignition problem. This may well be the most common cause for code 44. Before you do anything you check the ignition, try just replacing distributor cap and rotor , spark plug wires, and spark plugs. - Its cheap and easy and maintenance anyway. It might be possible that a misfire resulted in fouling of the oxygen sensor (code 26), then when replaced with a new one you got code 44.

Conditions for flagging...

- Engine coolant temp above 167F,
- Throttle position under 3 volts,
- 450 engine revolutions in a row no oxy sensor switching.

Possible faults:

- Fuel pressure fault,
- Stuck open purge valve,
- Poor ground connections,
- Poor oxy sensor ground connection,
- Open or short in oxy sensor heater and/or output circuit,
- Defective air injection pump or circuit,
- Intake air leak,
- Plugged fuel injector (or bad electrical connection)
- Defective maf sensor.

Do a hot engine vacuum reading. At about sea level, you should get roughly 20 inches of vacuum at hot idle.

You can have a vacuum leak in many impossible to see places....
- The egr system/pipes/valve,
- The vapor recovery system...at the vacuum port under the throttle (nipple falls out of manifold), at the charcoal canister hoses in the front air dam, intake manifold,
- Crankcase vent system, etc.

After that, check the fuel pressure and the injectors. You can unbolt the rail from the intake manifold and remove it, then remove each injector and check the intake screens. At that time, you can also remove the fuel pressure regulator and using air pressure, test the pressure set point. Should be 44 psi without any vacuum on the vacuum port. Fuel pressure typically runs between 32 to 44 psi, 44 psi full throttle (no vacuum), 32 psi with 20 inches of vacuum...


Ignition problems typically set a ff26. During a severe miss, fuel and air is dumped into the exhaust, setting the FF26. For FF44, the engine seems to not be able to get enough gas into the mixture. This means a shortage of fuel, or an abundance of air.

When heated with a torch till its hot and slightly glowing, the oxy sensor should put out about .9 volts. Voltage reading will vary around as you move the torch, but if it gets up to .9 volts, its ok.

I doubt they fail often, typically when the heater gets erratic. They have to be hot to work, so if they don't get hot, they don't work. The relay that powers the heater also runs the fuel pump.

You could have a big vacuum leak when the ecu operates the canister purge. The ecu will open the solenoid to purge the fuel vapors in the canister after the engine is up to at least 93F and above idle.


12.48 - Fuel Fail 48 : Idle Speed Control Valve ( Brett Gadzinsky,  )

The idle speed control valve adjusts the idle speed, something abnormal going on with the idle speed will be a sympton of problem as the ECM looks for the ISCV far out of position at idle.

Conditions for flagging ...

Throttle position...at idle
Engine coolant temp above 186F
ISCV full open
Engine speed lower than normal.
Or,
Engine coolant temp less than 94F
ISCV full closed,
Engine speed greater than normal.


Possible faults...

- Low battery voltage,
- Loss of ECM memory power,
- Loss of ECM ground connection,
- Badly mis adjusted idle bypass screw,
- Badly mis adjusted throttle,
- Air leak past ISCV,
- Low engine power at idle when hot,
- Stuck ISCV,
- Blocked ISCV port or hose.

The idle speed control valve adjusts the idle speed from a base idle speed, both up and down. Say the base idle speed is set for 500 rpm before the ISCV adjusts it...it can move the idle down 30 steps, and up 200 steps.

The ecu learns the correct default position and stores it if you start the engine cold, let it warm up fully without stepping on the gas, then drive off.

If the throttle is messed with, or the engine has a big vacuum leak, the ISCV will be at the end of its adjustment, or not be able to get the idle speed low enough, and set codes.

Many times, people who don't know fuel injection cars try to adjust the idle speed at the throttle. This will do nothing but cause problems till the ISCV runs out of adjustment, then the idle speed will start changing.

I would guess you just have to have the idle speed set up, or a vacuum leak fixed and all will be well.


 

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