Exhaust Back Pressure (EBP) Sensor

1997 PCED OBDII-Diesel

SECTION 5C: Pinpoint Tests

H: Exhaust Back Pressure (EBP) Sensor

H: Introduction

H1 DIAGNOSTIC TROUBLE CODE (DTC) P0470

DTC P0470 indicates an EBP sensor malfunction was detected during KOEO On-Demand Self Test.
Possible causes:

damaged EBP sensor
open signal ground
damaged PCM

NGS Tester installed.
Key on/engine off.
Select EBP Pid from the PID/DATA monitor menu on NGS Tester.

Is EBP reading below 127 kPa (18.5 psi)?

Yes	No
CLEAR DTC and RERUN KOEO On-Demand Self Test. If code is still present, REPLACE PCM.	GO to H2.

H2 SIGNAL GROUND CIRCUIT CHECK

Key off.
Disconnect EBP sensor connector.
Inspect for loose, damaged or pushed out pins. Repair as necessary.
Measure resistance from Pin A [Circuit 359 (GY/R)] to chassis ground.

Is resistance less than 5 ohms?

Yes	No
REPLACE EBP sensor. CLEAR DTCs and RETEST.	REPAIR open in signal return Circuit 359 (GY/R). CLEAR DTC and RETEST.

H3 CONTINUOUS DIAGNOSTIC TROUBLE CODE (DTC) P0470

Continuous DTC P0470 indicates an exhaust back pressure malfunction was detected during normal driving conditions.
Possible causes:

damaged EBP sensor
damaged connection
damaged PCM

NGS Tester installed.
Select EBP Pid from the PID/DATA monitor menu on the NGS Tester.
Observe the PID while performing the following:

Grasp the vehicle harness close to the EBP sensor connector.
wiggle and shake the vehicle harness while working toward the PCM.

Does the EBP reading fluctuate?

Yes	No
ISOLATE intermittent connection problem. CLEAR DTCs and RETEST.	GO to H4.

H4 CONNECTOR INSPECTION

Disconnect EBP sensor connector.
Inspect connector terminals and sensor terminals for signs of poor connection or corrosion.
Inspect connections at the 42-way and PCM connectors.

Are all connections good?

Yes	No
Unable to verify problem at this time. CLEAR DTCs.	REPAIR connection concern as required.

H5 DIAGNOSTIC TROUBLE CODE (DTC) P0471

DTC P0471 indicates an EBP range/performance problem was detected during normal driving conditions when EBP is enabled.
Possible causes:

damaged EBP sensor
plugged or restricted sensor supply tube
EPR linkage or butterfly damage
damaged PCM

Perform KOER On-Demand Self Test. If codes are present, repair them before continuing.
NGS Tester installed.
Select EBP Pid from the PID/DATA monitor menu on the NGS Tester.
Road test vehicle performing hard accelerations while monitoring the PID.

Does EBP increase and go above 25 psi with EBP device on?

Yes	No
Unable to duplicate failure. CLEAR DTC and RETEST.	GO to H6.

H6 INSPECT FOR EXHAUST LEAKS

Inspect turbo pipe, crossover pipes, and exhaust manifolds for leaks.

Are exhaust leaks present?

Yes	No
REPAIR exhaust leak and RETEST system.	GO to H7.

H7 SENSOR SUPPLY TUBE CHECK

Inspect the EBP sensor supply tube from the exhaust manifold to the sensor bracket for damage.
Verify tube is not plugged or restricted.

Is tube OK?

Yes	No
GO to H8.	REPLACE tube. CLEAR DTC and RETEST.

H8 EBP SENSOR CHECK

Disconnect EBP sensor connector.
Install ICP/EBP Adapter Cable D94T-50-A or equivalent between EBP sensor and vehicle harness.
Engine running.
Measure voltage between signal circuit and signal ground on ICP/EBP Adapter Cable D94T-50-A or equivalent.
Accelerate engine to WOT several times.

Is a minimum reading of 1.35v present during acceleration?

Yes	No
CLEAR DTC and RETEST. If code reappears REPLACE PCM.	REPLACE EBP sensor. CLEAR DTC and RETEST.

H9 DIAGNOSTIC TROUBLE CODE (DTC) P0472: EBP CIRCUIT LOW INPUT

DTC P0472 indicates EBP sensor circuit low input was detected during KOEO Self Test or during continuous diagnostic monitoring.
Possible causes:

open EBP sensor circuit
biased sensor/PCM
short to SIGN RTN or PWR GND on EBP sensor circuit
open in VREF circuit

Key off.
Disconnect EBP sensor connector.
Key on/engine off.
Measure voltage between Pin B Circuit 351 (BR/W) on harness connector and battery ground.

Is voltage reading 5v ± 0.5?

Yes	No
GO to H10.	REPAIR open in VREF Circuit 351 (BR/W).

H10 SIG RTN CIRCUIT CHECK

Measure resistance between Pin A Circuit 359 (GY/R) and ground.

Is resistance less than 5 ohms?

Yes	No
GO to H11.	REPAIR open in SIG RTN Circuit 359 (GY/R).

H11 EBP SIGNAL CIRCUIT CHECK

Key off.
Disconnect PCM. Inspect for loose, damaged or pushed-out pins. Repair as necessary.
Connect breakout box. Leave PCM disconnected.
Measure resistance between Pin 30 and Pin C Circuit 553 (P/LB) at EBP sensor harness connector.

Is resistance less than 5 ohms?

Yes	No
GO to H12.	REPAIR open in EBP signal wire Circuit 553 (P/LB). CLEAR DTCs and RETEST.

H12 VREF CIRCUIT CHECK

Measure resistance between Pin 90 and Pin B Circuit 351 (BR/W) at EBP sensor harness connector.

Is resistance less than 5 ohms?

Yes	No
GO to H13.	REPAIR open in EBP VREF (Circuit 351 [BR/W]). CLEAR codes and RETEST.

H13 GROUNDED EBP SIGNAL CIRCUIT CHECK

Measure resistance between Pin 30 and Pins 25/91/51/76/77 and 103.

Is resistance greater than 10,000 ohms?

Yes	No
GO to H14.	REPAIR short to ground in EBP signal wire Circuit 533 (P/LB). CLEAR DTCs and RETEST.

H14 CHECK FOR INTERNAL PCM SHORT ON PIN 30

Connect breakout box to PCM.
Measure resistance between Pin 30 and Pins 25/91/51/76/77 and 103.

Is resistance greater than 10,000 ohms?

Yes	No
REPLACE EBP sensor. RERUN Scan Tool Diagnostic Test.	REPLACE PCM. REMOVE breakout box. RECONNECT EBP sensor. RERUN Scan Tool Diagnostic Test.

H15 DIAGNOSTIC TROUBLE CODE (DTC) P0473

DTC P0473 indicates EBP sensor circuit high input detected during KOEO On-Demand Self Test or during continuous diagnostic monitoring.
Possible causes:

biased sensor/PCM
EBP circuit shorted to VREF
induce opposite DTC

Key on/engine off.
Disconnect EBP sensor.
Perform KOEO On-Demand Self Test.

Does DTC P0472 appear?

Yes	No
REPLACE EBP sensor. CLEAR DTCs and RETEST.	GO to H16.

H16 CHECK SHORT TO POWER ON PIN 30

Disconnect PCM. Inspect for loose, damaged or pushed-out pins. Repair as necessary.
Connect breakout box. Leave PCM disconnected.
Measure resistance between Pin 30 and Pins 90/97/71/55.

Is resistance greater than 10,000 ohms?

Yes	No
Internal PCM failure. REPLACE PCM. CLEAR DTCs and RETEST.	REPAIR short to power in EBP signal Circuit 553 (P/LB). CLEAR DTCs and RETEST.

H17 CONTINUOUS DIAGNOSTIC TROUBLE CODE P0478

DTC P0478 indicates an excessive back pressure condition existed during normal driving.
Possible causes:

stuck butterfly
restricted exhaust
plugged EBP sensor line
misadjusted EPR linkage

Key on/engine off.
Visually inspect butterfly tang.
(Refer to Section 4C, Diagnostic Routines, Performance Diagnostic Procedures, Exhaust Restriction for exhaust back pressure regulator tang position illustration.

Does tang reflect an open position?

Yes	No
GO to H18.	REPAIR damaged linkage or butterfly valve as required. CLEAR DTCs and RETEST.

H18 EXHAUST RESTRICTION CHECK

NGS Tester installed.
Select EBP PID from the PID/DATA monitor menu on the NGS Tester.
Engine running.
Accelerate engine to WOT while observing NGS Tester reading.

Is EBP reading below 193 kPa (28 psi)?

Yes	No
GO to H19.	REPAIR restricted exhaust. CLEAR DTCs and RETEST.

H19 EBP SYSTEM CHECK

Engine cold. EOT below 21°C (70°F) and IAT below 7°C (45°F).
Road test vehicle while monitoring EBP reading on the NGS Tester.
Observe reading while back pressure device is on.

Does NGS Tester reading stay below 345 kPa (50 psi)?

Yes	No
REPLACE PCM. CLEAR DTCs and RETEST.	CHECK EPR linkage adjustment. REFER to the Powertrain/Engine Group in the Service Manual.