Repair BS III Vehicles

 TROUBLE SHOOTING of BS III vehicle:

The repair of BS III vehicles is too difficult for a normal mechanic and will tired, to find out the defect of the vehicle. The BS III vehicle’s mechanic should be an electromech, and he must have a better knowledge of electrician. Some technical tips received from TATA motor regarding repair of BS III vehicles are as under, and I hope it will helpful to all workshop as well as technical persons those who are in the field.

CHECK ENGINE lamp blinks, Engine stops – Check diesel in tank, rectify air lock if any. Also check electrical fuses and replace with correct rating Fuse only. If complaint still remains, immediately report to Dealer/TASS.

CHECK ENGINE lamp blinks, Engine does not stop – Take the vehicle to the nearest workshop.

CHECK ENGINE lamp blinks, Limp-home mode- Vehicle can be driven at slow speed to nearest workshop.

CHECK ENGINE lamp does not blink, Engine stops – Check mechanical causes for diagnosis & report to Dealer/TASS

CHECK ENGINE lamp remains ON continuously – No fault on BS III engine. Take vehicle to the workshop.

Diagnosis for ENGINE COMPLAINTS

1)    engine cranks, but does not start:

A.	Check for mechanical causes:
	i	Fuel System: Clogged filters, strainers, electrical feed pump, air lock.
	ii	Diesel quality: drain water separator.
	iii	FIP: timing, calibration.
B.	“CHECK ENGINE” lamp: For a healthy vehicle, as soon as the ignition is ON, the check lamp on instrument cluster should glow for a few seconds and then go OFF after initialization of ECU. However if the check engine  lamp continuous to blink when the ignition key is in ON position, there is an error in EDC system. Connect the diagnostic tester and read errors in the ECU. Rectify errors as per instructions in diagnostic tester and probable causes given below.
	a)	Connectors of wiring harness:
		i       Check wiring harness connectors to sensors and actuators.
		ii      Fly wheel housing: Engine speed sensor.
		iii     FIP: HDK unit, timer device, Fuel shut off solenoid.
		iv    Injector: Needle lift sensor
	b)	Check ground points. Refer to circuit diagram given in Operator Service Book for more details on location of ground points.
	c)	Inspect wiring harness for any damage due to fouling or burn.
	d)	Check for battery voltage. ECU functioning is normal within 9-14 volts for 12V battery and18-26 volts for 24V battery.  Note: Check Battery voltage at Battery terminals, Starter motor terminals, and then ECU pin No. 4.
C.	Check all Relays  of ECU circuit :
	a)	Main Relay (Blue colour, common for 12V and 24 V system): Check polarity. If found to be reversed, the diode in the relay will surge the coil there by preventing the engine from starting. If this 12V, 20A relay with diode, part no. is 2632 5420 4602, is found defective, replace the relay.
	b)	Check 24 V Ignition relay – Yellow colour (for 24 V system)
	c)	Check 12 V Hold relay - Black colour. (for 24 V system).
	d)	Check continuity of Main Relay as below;-
		Check continuity between i)      Pin 3 of  Main relay and pin 18 of ECU ii)     Supply of 12 volts +ve and at pin 1 of Main Relay Note: Chattering noise from the relay indicates the supply is not building sufficiently for coils in relay to establish connections.
D.	Fuse:
	a)	Fuses of correct specifications
	b)	Bypassing the blown off fuse by using external copper wires will seriously damage electronic components of ECU.
	c)	Check supply of 12 V at Fuse and continuity between ECU fuse terminal to pin 18 ECU
		Note: After replacing the fuse, check cause of high current flow if there is a repeat blowing of fuse. A sharp pin has to be used to access the connector pins of ECU connectors as the multimeter probes cannot be inserted. Ensure ignition key is OFF before removing ECU connectors. Remove ECU connectors by pulling the locking sleeve away from connector.
E.	Engine Speed sensor: Mounted on Flywheel Housing / Clutch housing.
	a)	Wiring harness: Check connections to engine speed sensor on the clutch housing. Visually inspect the wiring harness for any external damage
	b)	Continuity check: Ensure ignition key is OFF and battery cut off switch is OFF while checking continuity. Multimeter range should be on mΩ.  Check continuity between:
		Pin No. on engine speed	Pin no. on ECU sensor
		1	102 ECU
		2	110 ECU
		3	86 ECU-Shield
	c)	Check sensor resistance 860+/- 10% W across pin 1 and 2.
	d)	Engine Speed sensor gap:
		i.           Maintain gap of 0.5 to 1.5 mm between sensor and flywheel. Measure the depth at fly wheel housing speed sensor from matching face to flywheel and then length on sensor from joining surface of flange to sensor element. The difference between the two should be 0.5 to 1.5 mm. ii.            Clean the transuding surface of the sensor for any greasy/oily deposits without damaging the sensor.
F.	Fuel Injection Pump (FIP)
	a)	Wiring harness to FIP: Check connections and visually inspect the wiring harness.
		i.            HDK unit 7-pin connector. ii.           Timer device 2-pin connector. iii.          ELAB –Fuel shut off solenoid.
	b)	Check supply to actuators: Use Chassis as ground(GND). Check when ignition key is ON
		i.           HDK unit 7-pin connector supply 12 V +ve at pin no. 7 ii.          Timer device 2-pin connector supply 12 V +ve at pin no. 1 iii          ELAB –Fuel shut off solenoid supply 12 V +ve
	c)	Continuity check:
		HDK unit 7-pin connector to ECU.                    Ensure no short connections between pins 1,2,3 & 4.  HDK 7- pin connector         Pin1 – ECU pin 108         Pin 2- ECU pin 107         Pin 3 – ECU pin 106         Pin 4 – ECU pin 116         Pin 5 – ECU pin 103         Pin 6 – ECU pin 111         Pin 7 – ECU pin 2(10A fuse)   (Pin nos are engraved  on the  connector)  ECU side       Timer device 2-pin connector to ECU. Also check for resistance 15W of timer solenoid.               Pin1 – ECU pin 2(10A fuse)               Pin 2- ECU pin 114.             Continuity of ELAB is to be tested with PIN 120 of ECU connector.
G.	Diode: (Placed between ignition switch and DC-DC converter, at dash board). This is applicable only for BS III engine with 24 V battery supply.
	a)	Check diode in DC DC converter circuit.                  Note: Diode faults                  i.      Open circuit faults: Engine will not start.                  ii.     Closed circuit faults: Engine can start but will not shut down with Ignition key.                    iii.     Diode is getting heated: Check 12V hold relay connection, if found wrong replace relay.

 2)    Engine does not stop even after removing the ignition keY.

             

A.	Fuel shut off solenoid not shutting down:
	a)	Check Blocking Diode on alternator for correct functioning, if not OK, replace.
	b)	Check for solenoid plunger stickiness, or malfunctioning. The plunger needs to be replaced in case found defective.
B.	On 24 V system vehicles, check diode near DC DC converter for correct function for close  circuit fault. Replace diode if found defective.
C.	Check Ignition relay and main relay for correct function. Replace if found defective.

3)    Sluggish pick up:

A.	Check for mechanical causes:
	a)	Chocked air filter, loose and broken joints of air intake, torn hoses, punctured pipes, leaky inter cooler, kinks.
	b)	Brake binding, wrong exhaust brake fitment, clutch slippage
	c)	Clogged fuel filters & strainers, electrical feed pump, air lock.
	d)	FIP: FIP timing, calibration.
B	If the CHECK ENGINE lamp blinks continuously when the ignition key is in ON position, connect the diagnostic tester and read errors in the ECU. Rectify errors as per diagnostic tester instructions.
C.	Check Boost pressure and boost air temperature sensor:
	Check wiring harness and connector to boost pressure for any external damage. Check whether the sticker on boost pressure sensor removed. If found damaged, replace sensor Boost pressure value should be >1275 mbar and can be checked with diagnostics tester.  If boost pressure is less, check for:
	a)	Blocked air filter
	b)	Air intake system- restrictions and kinks of hoses, hose clamps.
	c)	Turbocharger function
	d)	Intercooler – leakages and blockage of fins
	e)	Cylinder head cover gasket and mounting.
	f)	Boost pressure & Air temperature sensor: do following;-
		Check Supply voltage to sensor using multimeter. (Pins 1(ground) and    3 for 3-5 volts.)
		Check resistance values across pin 1 and 2 for 2.5 kW. High resistance values in MΩ indicates faulty temperature sensor.
		Continuity check: Boost pressure sensor with ECU connector.
		Ensure no short between pin 2 & 3 and pin 1 & 2.
		PIN 1 – ECU pin 76
		PIN 2 – ECU pin 75
		PIN 3 – ECU pin 63
		PIN 4 – ECU pin 68
		Note: Keep ignition key OFF while disconnecting sensors and checking continuity.
D.	Vehicle speed sensor:
	a)	Wiring harness: Check connections ( 3-pin pig tail connectors) to sensor on the gear box speedometer cable. Visually inspect the wiring harness for any external damage
	b)	Check mounting of vehicle speed sensor with speedometer cable and drive pin of sensor. (NOTE: Fuel quantity to be delivered is reduced to 80% because of discontinuity in vehicle speed sensor connections)
	c)	Continuity check:  (Keep Ignition key ON)
		Pin 1 – Ground (continuity with chassis Long Member)                          Pin 2 – ECU positive (12V with chassis as ground)                          Pin 3 – ECU pin 20
	d)	Supply to vehicle speed sensor should be 12V. Check voltage across pin 2 and pin 1

4)    Maximum fuel quantity limitation: Check parameters values in the diagnostic tester. The actual parameter values should be checked by running the engine and checking for fuel delivery values. Limiting fuel quantity can be reduced / increased by maximum of 5% to factory set value.

5)    CHECK ENGINE lamp blinking:

A.	Blinking of CHECK ENGINE lamp indicates presence of errors in the system. The errors can be read using a diagnostic tester and rectified accordingly.
b.	Blinking of CHECK ENGINE lamp without any errors in the system:
	a)	Check the circuit of diagnostic lamp. Continuity with ECU pin 80.
	b)	Fuse: Check vehicle speed sensor and CHECK ENGINE lamp 5A fuse.
	c)	Check for the correct bulb specifications (2W, not more) of the CHECK ENGINE lamp. Note: Every time the ECU is initialized by switching ON the ignition key, the ECU checks functionality of CHECK ENGINE lamp. The lamp should glow for a few seconds and then go OFF. During this process if excess of current is drawn by the bulb to glow or by any load in the circuit connected to diagnostic lamp, this will be recognized by the ECU as short circuit.
	d)	Supply of 12 V at CHECK ENGINE lamp and fuse.
	e)	Perform actuator test to check working of CHECK ENGINE lamp.

6)    CHECK ENGINE continuously ON:

a)	Check continuity of ECU pin 20 with CHECK ENGINE lamp –ve for short circuit fault.
b)	Check if CHECK ENGINE negative is short with chassis ground(GND)

7)    FIP timer chattering from timing device of FIP when ignition key is in ON position:

When ignition key is switched ON (engine has not started yet); FIP timer makes a chattering noise. This noise is kept intentionally audible for ascertaining functioning of FIP timer solenoid unit.

8)    Erratic vehicle behavior, stops when pressing brake pedal, low idle not stable, engine stalls during shifting to lower gear:

A.	Check ECU data set using diagnostic kit.  Replace ECU if incorrect.
B.	Check for Errors using diagnostic tester. ( Note; of EC: Replacement ECU ordering is to be done through TML Container number (part number U).

9)    Vehicle does not start after shutting down on its own:

a.	Check for mechanical causes:
	a)	Fuel System: Clogged filters, strainers, electrical feed pump, air lock, high pressure lines.
	b)	Battery (low voltage).
	c)	Starter, starter relay, alternator, etc.
b.	ECU initialization: If the engine is switched off by itself, ECU switches over to recovery state from operational state. By turning the ignition key to complete OFF position and re-cranking the engine will enable the ECU to switch over from recovery state to initialization state.
c.	Check ECU relay, Ignition relay and Hold relay
d.	Check if CHECK ENGINE is blinking. Check errors using diagnostic tester.
e.	ECU conducts self tests on the fuel shutoff solenoid after 100 hrs of operation. This test is done while the vehicle is in operation. In case if the fuel shut off solenoid does not pass the test, the engine will shut down by aborting any fuel supply. Error will be reported to diagnostic tester.           Note: By removing the plunger of fuel shut off solenoid will cause the solenoid to fail the self test by ECU. The vehicle    would shut down denying any fuel supply to engine unless the fuel shut off solenoid is made functional.

 10) Engine shuts off intermittently, even though diesel level is OK

a.	Check for mechanical causes:
		Fuel System: Clogged filters, strainers, electrical feed pump, air lock, high pressure lines.
B.	Check if CHECK ENGINE is blinking. Check errors using diagnostic tester.
	a)	Inspect ELAB
	b)	Check for any plausibility errors of Engine speed sensor, NBF

11) Engine jerky:

a.	Check if CHECK ENGINE is blinking. Check errors using diagnostic tester.
b.	Check connections to FIP timer solenoid (2 pole connection on FIP) and / or NBF sensor (1st injector)
c.	Check continuity across Wiring Harness of Needle lift sensor (NBF). Check for resistance value across pin1 and pin 2 of sensor for of 100W
		Pin 1 – ECU pin 109
		Pin 2 – ECU pin 101
d.	Check timer solenoid. Perform actuator test using diagnostic tester.

 12)  White smoke

a.	Check for various mechanical causes of white smoke.
	a)	Contaminated fuel used.
	b)	Fuel system- chocked fuel filter, feed pump, clogged injectors, correct size and length of high-pressure line etc.
	c)	FIP mounting flange bolts loose & timing disturbed.
	d)	Coolant leaking into combustion chamber.
	e)	Check FIP timing and calibration.
	f)	Contaminated fuel used.
b.	Check for start fuel quantity. Ensure incremental value assigned to parameter for start quantity is set to zero using diagnostic tester.
c.	Check for correct data set ID using diagnostic tester under ‘Read ECU data’.
d.	Check working of timer device by doing actuator test. On performing the actuator test on running engine, the engine noise will change on working of timer device.
e.	Check for ECU errors with diagnostic tester on Boost pressure sensor, water temperature sensor. Read the coolant temperature as reported in parameter values of the diagnostic tester. Faulty signals indicating low boost pressure / coolant temperature would prompt the ECU to deliver more fuel.
f.	Check coolant temperature sensor continuity. Check resistance 1.5 kW.
		Pin 1: ECU pin 112
		Pin2: ECU pin 104
g.	Check boost pressure sensor
h.	Check Accelerator pedal module

13) Engine speed is not increasing beyond idling

a.	Check for accelerator pedal module connections and mounting for external damage.
b.	Check for any errors reported on Accelerator Pedal Module.
c.	Check supply 5V between pins 2 & 3. Accelerator Pedal Module – (pins market 1 to 6  on the wiring harness side connector).
d.	Check for resistance values of
	a)	Potentiometer-1 (1.2 k Ω) at pin 3 and2 and Potentiometer-2 (1.7 k Ω) at pin 5 and 1, ( Use multimeter across the pins.)
e.	Mount the APM suitably and check for resistance variation in multimeter while pressing the APM from 0% to 100% travel.
f.	Check the accelerator working function on diagnostic tester. Connect the diagnostic tester and go in “Check Parameters”. Select accelerator pedal and check values. As the pedal is getting pressed, the % value increases. Potentiometer 1 resistance variation – pins 3 and 4 Potentiometer 2 resistance variation – pins 5 and 6       Continuity of Accelerator Pedal Module:
		APM Pin                       ECU PIN     1                                         31     2                                        12     3                                        50     4                                        69     5                                        51     6                                        70

14  Black smoke:

a.	Check for various mechanical causes:
	a)	Contaminated fuel used.
	b)	Check clamps of intake hoses from Air filter > turbo charger > intercooler > Intake manifold. Check for damaged/punctured hoses.
	c)	Fuel system- chocked fuel filter, feed pump, injector dribbling, correct size and length of high-pressure line, etc.
	d)	Check for brake binding, wrong exhaust brake fitment.
	e)	Check FIP timing and calibration.
	f)	Check for poor compression pressure.
b.	Check  boost pressure sensor and coolant temperature sensor.
c.	Check ECU Data set ID using diagnostic tests under ‘Read ECU Data’.

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