Service Exhaust Fluid System Message GM trucks

Service Exhaust Fluid P203D P21AB or P21B0

GM has issued service bulletins #PIP4887A and #12-06-04-002E to address a Service Exhaust Fluid System Message and trouble codes P203D, P21AB, or P21B0 on the trucks listed below. If you see the “Service Exhaust Fluid System” and a “See Owner’s Manual Now” message displayed on the instrument cluster and scan the vehicle and find trouble codes P203D, P21AB, and P21B0, this bulletin may apply to you.

P203B  –  Reductant Level Sensor Performance, The ECM receives a serial data message from the reductant sensor module that the reductant level sensor indications are not plausible

P203C  –  Reductant Level Sensor 1 Circuit Low Voltage. The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is less than 0.17 V for greater than 3 s. A voltage within this range indicates a short to ground.

P203D  –  Reductant Level Sensor 1 Circuit High Voltage.  The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is between 3.56-4.74 V for greater than 3 s. A voltage within this range indicates an open circuit, or
The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is greater than 4.74 V for greater than 3 s. A voltage within this range indicates a short to voltage.

P21AA  –  Reductant Level Sensor 2 Circuit Low Voltage. The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is less than 0.17 V for greater than 3 s. A voltage within this range indicates a short to ground.

P21AB  –  Reductant Level Sensor 2 Circuit High Voltage. The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is between 3.56-4.74 V for greater than 3 s. A voltage within this range indicates an open circuit, or
The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is greater than 4.74 V for greater than 3 s. A voltage within this range indicates a short to voltage.

P21AF –  Reductant Level Sensor 3 Circuit Low Voltage. The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is less than 0.17 V for greater than 3 s. A voltage within this range indicates a short to ground.

P21B0  –  Reductant Level Sensor 3 Circuit High Voltage. The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is between 3.56-4.74 V for greater than 3 s. A voltage within this range indicates an open circuit, or
The ECM receives a serial data message from the reductant sensor module that the emission reduction fluid tank level sensor 1, 2 or 3 voltage is greater than 4.74 V for greater than 3 s. A voltage within this range indicates a short to voltage.

Models Affected by PIP4887A

2010-2011 Chevrolet Express, Silverado
2010-2011 GMC Savana, Sierra
Equipped with 6.6L Duramax Diesel Engine RPO codes LML or LGH

What the Service Exhaust Fluid P203D P21AB or P21B0 means

The reductant tank has a level/temperature sensor inside that tells the ECM the reductant level and temperature. The level/temperature sensor gets power from the underhood electrical center and grounds through a chassis ground circuit.

The level sensor has three sensing elements. Reductant level sensor 3 is highest, reductant level sensor 2 is located between sensor 1 and 3. Reductant level sensor 1 is located at low reductant level. Reductant level sensor 3 is located at less than half range of the DEF tank level.

The reductant sensor module converts the analog data to a digital serial message to the ECM.

Diagnose Service Exhaust Fluid message

Using a digital meter, check the resistance of the

Reductant tank heater

reductant tank heater #1. Disconnect the Glow Plug Control Module and check the resistance reading on pin 11 (orange/white) and ground. You should see 2-4Ω. If the tank heater resistance is off, replace the heater. After replacing the heater, use a scan tool to perform a reductant fluid tank level reset. Then perform a reductant system leak test. The system must hold 61-83-psi. Finally, use a scan tool to command each of the heaters on, one at a time for at least 10-seconds each.

©, 2020 Rick Muscoplat