Introduction Jake Brake - Jacobs Vehicle Systems Engine .

Jake Brake Troubleshooting: DDEC II Controls IntroductionThese instructions are applicable for Jake Brake Models71/92A, 750, 760, 760A and 765.The Jacobs Electronic Control Module, P/N 017179, isa sealed electronic device and is not field serviceable.The Control Module can be operated using the standarddash toggle switches or the Jacobs Dash Switch Module,P/N 017328 or 017346. To test if this device requiresreplacement, follow the step-by-step procedures withinthe troubleshooting guide.Equipment Required for Testing: Voltmeter with 20,000Ohm/volt input impedance, minimum. Keep the voltmeteron the 20 VDC/div scale for the 12-volt control and 200VDC/div scale for the 24-volt control for all testmeasurements.NOTE:THIS CONTROL CAN BE USED FOR 12- OR24-VOLT OPERATIONS. USE 12/24 VOLTSWHEN REFERRING TO THE ( ) BATTERYVOLTAGE. THIS GUIDE WILL MAKE REFERENCETO A 12-VOLT OPERATION. ACTUAL BATTERYVOLTAGE MAY VARY UP TO 2 VOLTS.If measuring the voltage at the solenoid valves, make surethat all wiring harnesses are connected. If the voltage atthe output of the control is measured without the solenoidvalves connected, both the BLUE and YELLOW wires willmeasure approximately 1 volt. These are internal voltagesestablished by the control module when the output wiresare disconnected.Operation FunctionThe in-line switch module (if used) is connected to thepower input side of the control. This is the harness withthe RED and GREEN wires, P/N 015708.The ON/OFF power switch connects the RED wire to the 12 volt vehicle electrical system providing power to thecontrol module.The PURPLE and GRAY inputs select which one of theDK BLUE or YELLOW outputs will be active. The (AUX LO)GRN/YEL, (AUX HI) ORANGE, (#508) BROWN, and(CLUTCH SWITCH) BLACK and WHITE inputs controlwhen the DK BLUE and YELLOW will be active. To allowthe outputs to be active, the following must be true:1.The clutch switch must be closed connectingthe BLACK and WHITE wires together.2.The (AUX LO) GRN/YEL wire must be connectedto ground (0 VDC).3.The (AUX HI) ORANGE wire must be connected to theWABCO ABS Interface. If the vehicle is not equippedwith ABS, the end of the wire should be insulated.Before active troubleshooting is begun, check the integrityof all wiring and harness connections to verify thatconnections are tight and that wires are not pinchedand do not have damaged insulation.

JAKE BRAKE MODELS 71/92A WIRING DIAGRAMDDEC SERIES II (2 MODE)CONTROL GROUP P/N 017363For Model 750 DDEC II (2-mode), use the wiring diagram forModel 71/92A and change the Harness, P/N 017378, to P/N 017370.Add the Harness, P/N 017393; Connector, P/N 014828; and UndercoverWiring, P/N 019098. Change the housing identification from “LEFT” and“RIGHT” to “REAR” and “FRONT”.015708HARNESSCLUTCHSWITCHDK BLUEYELLOWBLACK017179CONTROL MODULEBL/WHGRAYPINKGRAYPurple and gray wires maybe used by some vehiclemanufacturers. If not used,wires should be cut offand ends insulated.PURPLE017346 SWITCH GROUP(2-MODE)ONHIOFFBROWNWHITEREDINSULATEEND GEGRN/YELPURPLE 12VCONNECTGROUND TONEGATIVEBATTERY POSTOR ENGINEFRAME RAILNON-ATEC AUTOMATICTRANSMISSIONSUSE PRESSURE SWITCHTO ATEC ECM WIRE 211If ATEC is used,connect this wireto ATEC ECMWire 213.Cut off black wireand insulate end.No clutch switchis used with ATEC.TO DDEC ECM WIRE 508LONOTE: If dash switches areused instead of SwitchGroup, the 015708 Harnessmay be plugged directly in tothe Control Module and the017370 Harness is not used.LEFTBack side ofswitch moduleRIGHTENGINE BRAKE HOUSINGSFIG. 1MODELS 760, 760A AND 765 WIRING DIAGRAMDDEC SERIES II (3 MODE)RETROFIT/AFTERMARKET INSTALLATIONNon-ATEC**automatic transmissionsuse pressure 28 SWITCH GROUPInsulate endof orange wire*Purple and gray wires maybe used by some vehiclemanufacturers. If not used,wires should be cut offand ends insulated.CLUTCHSWITCHDK BLUEYELLOWBLACK017179CONTROL MODULEGRAYGROUNDIf not used,connect toground.017263HARNESSREDGREENORANGEGRN/YELPURPLE 12V015708HARNESSONHIMEDNOTE: If dash switches areused instead of SwitchGroup, the 015708 Harnessmay be plugged directly in tothe Control Module and the017263 Harness is not used.OFFLOIf ATEC is used,connect this wireto ATEC ECMWire 213.Cut off black wireand insulate end.No clutch switchis used with ATEC.BROWNFor WABCO ABS interface,see enginebrake/WABCO ABSinterfaceTO ATEC ECM WIRE 211TO DDEC ECM WIRE 508017392 UNDERCOVER WIRING014828CONNECTOR017393HARNESSYELLOWDK BLUEREARCENTERFRONTBack side ofswitch moduleENGINE BRAKE HOUSINGS* Orange wire for ABS. If no ABS is present, insulate end of wire.** ATEC: Automatic Transmission Electronic ControlledFIG. 22JAKE BRAKE TROUBLESHOOTING: DDEC II CONTROLS

Problem: Engine Brakewill not activate015708HARNESSProbable Cause: Check supply voltage 12VCONNECTGROUND TONEGATIVEBATTERY POSTOR ENGINEFRAME RAILGREEN/YELLOWINSULATEEND OFORANGEWIREProblem: Engine Brakewill not activate (cont.)2.REDGREENORANGEPURPLEGRAYCorrection: With the ignition switch on, disconnectthe P/N 015708 harness from the control moduleconnector. Measure the voltage at the RED wire.Place the positive probe ( ) of the voltmeter on theterminal of the RED wire and the negative probe (-)to ground. The voltmeter should read 12 VDC(Fig. 3). If this condition is not present, check thatsystem is energized and check power supply.FIG. 3Probable Cause: Check switches and connectionsa.Optional Selector Switch: Disconnect P/N 015708harness from control module. Measure voltageat both PURPLE and GRAY wires. With selectorswitch in HI position, both wires should read 12 VDC (Fig. 4). If this condition is not present,check power supply, connections and switches.Repair or replace as required.b.015708HARNESSCorrections:Jacobs Switch Group: Disconnect P/N 017263(017370) harness from Jacobs control module.Measure the voltage at the RED wire. Thevoltmeter should read 12 VDC when the mainpower supply is ON and 0 VDC with main powersupply OFF (Fig. 5). If these conditions are notpresent, check power supply and connections.Vm 12VCONNECTGROUND TONEGATIVEBATTERY POSTOR ENGINEFRAME TEEND OFORANGEWIREFIG. 4VmHARNESS017263 (017370)FIG. 5JAKE BRAKE TROUBLESHOOTING: DDEC II CONTROLS3

Problem: Engine Brakewill not activate (cont.)GRAYProbable Cause: Check clutch switch.Correction: With the P/N 015709 (017378) harnessconnected to the control module, measure the voltageat the terminal of the WHITE wire. With the clutchengaged (pedal not depressed), a reading of 0 VDCshould be measured. With the clutch disengaged(pedal depressed) a reading of 5 VDC /- 0.5 VDCshould be measured (Fig. 7). If this condition does notexist, check continuity of clutch switch and BLACK andWHITE wires.FIG. 6Probable Cause: Check engine brake enablesignal.Correction: Disconnect 015709 (017378) harnessfrom 017179 module. Start the engine. Turn theengine brake switch OFF. Place the positive probeof the voltmeter at the terminal of the BROWN wireand the negative probe on ground (Fig. 8). Increaseengine RPM to rated engine speed. The voltmetershould measure 12 VDC. Release throttle; voltageshould drop to 0 VDC. When the engine reaches idle,the voltage should again read 12 VDC. If the voltagedoes not change, check connections and wiring. Ifproblem continues, have the engine ECM checked.HARNESS015709 (017378)CLUTCHSWITCHDARK ued)(Fig. 6) With main power supply ON andselector switch in LO, the PURPLE wire shouldread 12 VDC and GRAY wire 0 VDC. Withselector switch in MED position, GRAY wireshould measure 12 VDC; PURPLE wire 0 VDC.With selector in HI position, both PURPLE andGRAY wires should measure 12 VDC. If theseconditions are not present, check connections,check wiring schematic for proper position ofwires to switch and/or replace switch.PURPLEProbable Cause: Check switches and connectionsb.3.VmRED2.017263HARNESSTO DDEC ECMWIRE 508FIG. 7HARNESS015709 (017378)CLUTCHSWITCHDARK BLUEYELLOWBLACKVmBLUE/WHITEBROWNWHITETO DDEC ECMWIRE 508FIG. 84JAKE BRAKE TROUBLESHOOTING: DDEC II CONTROLS

Problem: Engine Brakewill not activate (cont.)Vm5.Probable Cause: Check output.Correction: Inspect DK BLUE and YELLOW wiresleading to solenoid valve connectors. Check for loosecontacts, pinched wires or scraped insulation. Startthe engine, turn the engine brake switch ON andselect HI. Advance the throttle to rated speed andthen release the throttle. Voltage at both YELLOWand DK BLUE wires should measure 12 VDC (Fig. 9).YELLOWDARK BLUEREARCENTERFRONTENGINE BRAKE HOUSINGS6.Probable Cause: Check Jacobs control module.Correction: Measure the voltage at the ORANGEwire of the control module. With system power ON,the voltage should measure 5 VDC /- 0.5 VDC(Fig. 10). If this condition is not present, replacemodule.FIG. 9015708HARNESS5V 12VCONNECTGROUND TONEGATIVEBATTERY POSTOR ENGINEFRAME RAILREDGREENORANGEPURPLEGRAYNOTE:WHEN MEASURING VOLTAGE, CHECK THATALL HARNESS CONNECTIONS ARE TIGHT. IFTHE VOLTAGE IS MEASURED WITH THEHARNESS FROM THE SOLENOID LOOSE ORDISCONNECTED, BOTH THE DK BLUE ANDYELLOW WIRES WILL MEASUREAPPROXIMATELY 1 VDC. THIS IS ANINTERNAL VOLTAGE ESTABLISHED BY THECONTROL MODULE FOR REFERENCE.VmGREEN/YELLOWINSULATEEND OFORANGEWIREFIG. 10JAKE BRAKE TROUBLESHOOTING: DDEC II CONTROLS5

Problem: Engine Brakeperformance erratic1. 1ΩProbable Cause: Check ground connection.ΩCorrection: The resistance between the engine blockand the negative terminal of the battery must be lessthan 1 ohm (Fig. 11). The resistance between theGREEN wire of the engine brake control module andthe negative terminal of the battery must be less than5 ohms for proper module operation (Fig. 12).BATTERY If vehicle is NOT equipped with ABS system:The GREEN/YELLOW wire must be grounded,preferably to the same point as the GREEN wire.These wires should be isolated from other systemground wires. The ORANGE wire must not begrounded and must be insulated when not in use(no ABS).2.Probable Cause: Check undercover wiring.Correction: Make sure solenoid wires are securelyattached to the solenoid valves.3.Probable Cause: Check for solenoid failure.Correction: Measure resistance of each solenoidvalve (Fig. 13). Solenoid valves not within correctvalues must be replaced (see chart below).FIG. 11015708HARNESS 12VCONNECTGROUND TONEGATIVEBATTERY POSTOR ENGINEFRAME RAILREDGREENORANGE 5ΩPURPLEGRAYVehicles equipped with ABS system:Refer to specific ABS or vehicle manufacturer’selectrical wiring diagrams or consult a Jacobsdistributor for more information-GREEN/YELLOWΩINSULATEEND OFORANGE WIREBATTERY -FIG. 12RESISTANCE (OHMS)COLDHOTP/NVOLTAGE016440*12 VDC9.62 to 10.7511.8 to 14.3016441*24 VDC31.5 to 38.538.2 to 50.0016442*24 VDCD/L31.5 to 38.538.2 to 50.0020239*12 VDC9.0 to 10.011.5 to 14.001867412 VDC9.5 to 10.511.5 to 14.0013472*24 VDCSCREW34.9 to 38.743.3 to 51.3003784,004205,003433,00268912 VDC19.8 to 22.024.0 to 29.5003784,004205,003433,00268924 VDCΩ*D/L6FIG. 1319.8 to 22.024.0 to 29.5Current Production Solenoid ValvesDual LeadJAKE BRAKE TROUBLESHOOTING: DDEC II CONTROLS

NOTESJAKE BRAKE TROUBLESHOOTING: DDEC II CONTROLS7

Jacobs and Jake Brake are registered trademarks andD-Lash is a trademark of Jacobs Vehicle Equipment Company22 East Dudley Town Road Bloomfield CT 06002 1995 Jacobs Vehicle Equipment CompanyPrinted in USA 12/95P/N 021772

4. Probable Cause: Check engine brake enable signal. Correction: Disconnect 015709 (017378) harness from 017179 module. Start the engine. Turn the engine brake switch OFF. Place the positive probe of the voltmeter at the terminal of the BROWN wire and the negative probe on ground (Fig. 8). Increase engine RPM to rated engine speed. The voltmeter