Categories: Truck Repair

Paccar Truck Primary Air Pressure Gauge Inoperative Trouble Guide

Here is a instruction show you guide on how to repair Paccar truck DTC11703 & DTC11704 primary air pressure gauge inoperative trouble.

Preparations:

Paccar ESA Electronic Service Analyst v5.4.3 v5.2.2 Free Download

Symptom:

Primary air pressure gauge inoperative.

All other gauges are operational.

The Primary Air Pressure Gauge uses an electronic transducer (sensor) which monitors system air pressure and converts it into a voltage output that is sent to the instrumentation system.

The output voltage of the sensor is proportional to the pressure it is sensing.

The following procedures have been developed to assist the technician in diagnosing multiplexed instrumentation problems using the Electronic

Service Analyst (ESA) hardware/software diagnostic tool. It is assumed the service technician performing instrumentation repairs is knowledgeable about how to use ESA.

Procedure:

Step 1:

Turn ignition key ON.

Start ESA, then select“Connect” to establish communication to the vehicle

Step 2:

elect ‘Monitor”.From the“Components”window, select “Primary

Air Pressure”,then select “Open.

Gauge graphic on screen displays reasonable reading

Go to Step 3.

Gauge graphic on screen does not display reasonable reading

Go to Step 4

Step 3:

Select “Simulate”. Drag the “Value” bar until the pointer on the gauge image is approximately mid-scale. Observe vehicle gauge movement.

Vehicle gauge does not move. Go to Step 3-1

Vehicle gauge reading is in the same range as the ESA gauge image. Go to Step 3-7

Perform the following checks:

NOTE: For vehicles with a CECU, use the “Program” feature in ESA to make sure that the parameter for the inoperative gauge is enabled.

An inoperative gauge may simply have its CECU parameter set to disabled.

1.Check CVSG data link wiring: Observe Gauge position in the wiring daisy chain.

a.If gauge is mounted between two other functioning gauges CVSG data link wiring is OK. Go to Step 3-5

b.If gauge is last gauge in daisy chain or followed by other non-functional gauges, go to Step 3-2.

2.Check continuity between Pin 1 on gauge harness connector and Pin 14 of the 52 Pin ICU/CECU connector C.

3.Check continuity between Pin 3 on gauge harness connector and Pin 15 of the 52 Pin ICU/CECU connector C.

4.Repair daisy chain jumper harness as necessary.

5.Once continuity on both wires exists, perform “Simulate” test again.

a.If gauge functions properly during “Simulate” test, repair is complete.

Return truck to service

If gauge does not function during “Simulate” test, install a known good gauge and perform “Simulate” test again.

i.If gauge functions properly test is complete. Install new gauge permanently. Re-test and return truck to service.

If gauge does not function during “Simulate” test, install Test ICU/CECU and perform “Simulate” test again.

(1) If gauge functions properly test is complete. Install new ICU/CECU permanently. Re-test and return truck to service.

(2) If gauge does not function properly during “Simulate” test,replace gauge.

6.Once gauge is replaced

a.Verify gauge functionality.

b.Return truck to service.

7.Is this a recheck after Step 5, Step 6 or Step 7?

a.Yes. Return truck to service.

b.No, Gauge and CVSG data link wiring is not the problem. Go to Step 4

Step 4:

Select “Diagnose” to view “Active” primary air pressure gauge diagnostic trouble codes

No “Active” DTCs displayed

Indicates the problem could be a defective sensor, poor ground or no input or output voltage at sensor. Go to Step 5

DTC 11703 displayed – Open in primary air pressure circuit.

This DTC will be recorded when the control unit sees an open or short to ground at the primary air pressure sensor input. The fault is recorded when

the voltage at the input is below .1 volt

DTC 11704 displayed – Short in primary air pressure circuit

This DTC will be recorded when the control unit sees a short to +5V at the primary air pressure sensor input. The fault is recorded when the voltage at

the input is above 4.9 volts

Step 5:

Using a digital multimeter, check the ground, input and output voltages at the sensor connector.

Pin A – Ground

Pin B – Input Voltage

Pin C – Output Voltage

See Harness Interface

Diagrams for possible sensor locations.

See Connector

Identification for position and identification of the electrical connectors of ICU/CECU.

See ICU/CECU Pinout for terminal details of the ICU/CECU electrical connection

Sensor Ground) – There should be continuity between the sensor connector ground (Pin A) and a cab ground terminal. See MultiMeter Graphic below.

(Sensor Input Voltage) – Input voltage from ICU/CECU to sensor connector (Pin B) should be +5 volts. See MultiMeter Graphic below.

(Sensor Output Voltage) – Signal output voltage at sensor connector (Pin C) will vary depending on air pressure, but should be more than.1 volts and less than 4.9 volts.

See MultiMeter Graphic and Table below.

NOTE: Do not unplug sensor connector to perform sensor output voltage check. Slide connector seal back to expose terminal ends.

Use test leads with needle point tips to probe connector terminals.

Air Pressure

(PSI)

150

Output Voltage

(VDC)

4.75

2.50

2.05

1.15

0.25

NOTE: Make sure that the system you are testing has some pressure to measure.

Check for continuity between sensor connector Pin A and ground terminal.

a.If there is continuity between Pin A and the ground terminal, test is complete. Go to Step 5-2.

b.If there is no continuity between Pin A and the ground terminal:

i.Check for continuity between sensor connector Pin A and Pin 2 of the 52 Pin ICU/CECU connector C.

ii.Check for continuity between Pin 5 of the 9 Pin ICU/CECU connector A and a cab ground terminal.

iii.Repair wiring as necessary. Go to Step 2.

2.Check input voltage at sensor connector Pin B.

a.If there is voltage at Pin B, Go to Step 5-3.

b.If there is no voltage at Pin B, check for voltage on Pin 1 of the 52 Pin ICU/CECU connector C.

i.If there is voltage on Pin 1, check continuity between Pin 1 at ICU/CECU and Pin B at sensor connector. Repair wiringas necessary. Go to Step 2.

ii.If there is no voltage on Pin 1 at ICU/CECU, replace ICU/CECU.

Go to Step 2.

3.Check signal output voltage at sensor connector Pin C.

a.If there is no voltage at Pin C, replace sensor. Go to Step 2.

b.If there is voltage at Pin C, Go to Step 6

1.Connector Seal

2.Pin A

3.Pin B

4.Place MultiMeter Probe On Pin C

Step 6:

Select “Diagnose”to view primary air pressure gauge DTCs.

Next, unplug the primary air pressure sensor connector at sensor.

See Harness Interface

Diagrams for possible sensor locations.

See Connector

Identification for position and identification of the electrical connectors of ICU/CECU.

See ICU/CECU Pinout for terminal details of the ICU/CECU electrical connections

DTC 11703 – Open in primary air pressure circuit is displayed as “Active”.

Check resistance between Pin C and ground terminal.

a.If there is less than 5K ohms between Pin C and the ground terminal,

i.Check wiring for short from sensor to ICU/CECU. If short found,repair and go to Step 2.

Remove the 52 Pin ICU/CECU connector C and measure resistance between Pin 6 of the 52 Pin ICU/CECU connector C and ground terminal. If less than 5K ohms replace ICU/CECU and go to Step 2.

b.If there is more than 20K ohms between Pin C and ground terminal,

i.Check wiring for open from sensor to ICU/CECU. If open found, repair and go to Step 2.

ii.Remove the “C” connector from the ICU/CECU and measure resistance between Pin 6 of the 52 Pin ICU/CECU connector

C and ground terminal. If more than 20K ohms, replace ICU/CECU and go to Step 2

Step 7:

Select “Diagnose”to view primary air pressure gauge DTCs.

Next, unplug the primary air pressure sensor connector at sensor.

See Harness Interface

Diagrams for possible sensor locations.

See Connector

Identification for position and identification of the electrical connectors of ICU/CECU

DTC 11704 – Short in primary air pressure circuit is displayed as “Active”

If the fault is still “Active” after unplugging the sensor connector, you have confirmed there is a short. This sensor wire starts at pin 6 of the 52

Pin ICU/CECU connector C and ends at pin C on the sensor connector.

There is a short between the sensor wire and a power source wire. Some typical power wires to inspect are listed below (you may need to verify

any power source in the main cab harness:

See ICU/CECU Pinout for terminal details of the ICU/CECU electrical connections

Check for pinched or chaffed sensor and power wiring. Repair or replace wiring as necessary.Go to Step 2

DTC 11704 – Short in primary air pressure circuit is now displayed as “Inactive”

If DTC 11704 changes to “Inactive” after unplugging the sensor connector, you have confirmed the problem is a short to +5V in the sensor itself, not the wiring.

Replace sensor. Go to Step 2

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