Check Engine Fault Diagnosis

The following is intended to supplement JDS in its analysis of fueling failure codes. It details those fault codes that could be induced by mechanical problems as opposed to purely electrical faults.

Fault Code 11 Idle trim pot out of range.
(Static) This is purely electrical - Use JDS.

Fault Code 12 Air flow meter out of normal operating range.
(Static)
(i) Check air intake tract for blockage, particularly within the air meter venturi.

(ii) Check for signs of dust or salt contamination
in the air flow meter, particularly around the sensing element.

(iii) Check for signs of water saturation within the
air flow meter, may have been caused by driving through deep water or driving quickly through heavy storms. It should be possible to cancel this fault code as effect will only be temporary.
(iv) If fault code 12 coincides with an engine
misfire then check for faulty crankshaft sensor, toothed wheel and/or sensor to toothed wheel air gap.

Fault Code 14 - Coolant sensor out of range or resistance not
(Static) changing.

(i) Check coolant level.

Fault Code 16 - Air temperature sensor out of range.
(Static) This is purely electrical - Use JDS.

Fault Code 17 - Throttle potentiometer out of normal operating
(Static) range.

(i) Check security of throttle potentiometer mountings.

(ii) Check for signs of wear in potentiometer drive.

Fault Code 18 - Throttle pot/air flow meter comparison (air flow low).
(Dynamic)

(i) Check for air leak downstream of air flow meter.

(ii) If engine lacks power then check for blockage in
air intake or exhaust system.

(iii) Check for throttle pot stuck high - does idle speed
control operate and fuel cut off operate on overrun.

Fault Code 19 - Throttle pot/air flow meter comparison
(Static) (high air flow at idle).

(i) Check throttle potentiometer drive and its attachment to the throttle body
Note: An open throttle with the throttle pot still cause the engine speed to surge from 1000 to 1500 rpm and back under the action of fuel cut off.

Fault Code 22 - Fuel pump drive.
(Static)

(i) Inspect air pump circuit when in combination with code 66.

This is purely electrical - Use JDS.
Fault Code 23 - Fuel Supply (engine running too rich). (Dynamic)

(i) Check for excessive pressure in fuel rail - is vacuum pipe connected to pressure regulator.

(ii) Check for blockage in fuel return line (excessive

pressure after regulator).

(iii) Check fuel pressure regulator.

(iv) Check coolant temperature sensor for high resistance
(covered by JDS).

(v) Check for blockage in air flow meter venturi causing increased air flow through sensing duct.

(vi) Check for exhaust leak between manifold and lambda
sensor.

(vii) Check for purge valve stuck open - clamp pipe to prove.

Fault Code 24 - Ignition drive.
(Static) This is purely electrical - Use JDS.

Fault Code 26 - Air Leak (engine running excessively weak).
(Dynamic) Refer to Technical Bulletin sec. 18, no. 17.
(i) Check for air leaks into induction system, e.g. Vacuum pipe into air conditioning. Vacuum pipe to EGR valve. Vacuum pipe to fuel pressure regulator. EGR connections at valve and inlet manifold. Inlet manifold joint faces. Damaged intake elbow. Evaporative loss system vapor pipe. Vacuum pipe to fuel tank vent valve. Engine breather system.

(ii) Check for low pressure in fuel rail - regulator stuck
open, fuel pump vapor locked or fuel filter blocked.

(iii) Check that fault was not stored due to lack of fuel
in tank.

(iv) Check for restricted injector flow as a result of
nozzle gumming.
Fault Code 29 - ECU self check.
(Static) This is purely electrical - Use JDS (refer to Technical Bulletin section 18, number 14).

Fault Code 33 - Injector drive fault.
(Static) This is purely electrical - Use JDS.

Fault Code 34 - Injector leakage.
(Dynamic)
(i) Check for purge valve stuck open.

(ii) Check that purge valve is electrically connected and
closes after switching ignition off.

(iii) Check injectors for leakage. Pressurize fuel rail
while observing injectors for signs of dribble from nozzle. To pressurize fuel rail switch ignition on and off a number of times without cranking the engine.

Fault Code 37 - EGR drive.
(Static) This is purely electrical - Use JDS.

Fault Code 39 - EGR valve function.
(Dynamic)
(i) Check for vacuum signal to valve. Should only be present at above 1000 rpm with transmission in drive.

(ii) Check that valve lifts when vacuum applied.

(iii) Examine valve for damage, e.g., punctured diaphragm.

(iv) Check for blockage in transfer pipe or distribution
tube in inlet manifold.

Fault Code 44 - Lambda sensor fault.
(Dynamic) Refer to Tecbnical Bulletin sec. 18, no. 17.
Check for excessive richness or weakness outside the range flagged under fault codes 23 and 26.

Fault Code 46 - Idle speed control valve coil Number 1.
(Dynamic) This is purely electrical - Use JDS.

Fault Code 47 - Idle speed control valve coil Number 2.
(Dynamic) This is purely electrical - Use JDS.
Fault Code 48 - Idle speed control valve out of position.
(Dynamic)
(i) Check pipe connections to control valve for blockage.

(ii) Check for stuck control valve by operating air
conditioning or power steering, idle speed control should adjust for extra load.

Fault Code 66 - Air pump drive.
(Static) This is purely electrical - Use JDS.

Fault Code 68 - Road Speed signal.
(Dynamic) This is purely electrical - Use JDS.

Fault Code 69 - Drive/Neutral switch.
(Static) Refer to Technical Bulletin section 18, number 14.

(i) Check transmission selector cable adjustment.

(ii) Check rotary switch adjustment.