Antilock Braking System (ABS)

DTC 45 LF Valve Solenoid Malfunction:

CIRCUIT DESCRIPTION
With the ignition in "Run," "Bulb Test" or "Start," the EBCM applies voltage to the coil of the BPM valve relay. The EBCM will complete an internal self-check before providing ground to the coil. Once energized, the relay will provide B+ to the valve solenoids.

DTC 45 WILL SET WHEN
The expected position of the left front valve solenoid does not match the commanded position from the EBCM (if valve line voltage does not match expected value). Conditions which could cause DTC 45 to set are damage to the left front solenoid, an open or short to ground or battery voltage on CKT 826.

ACTION TAKEN
If a malfunction is detected which causes a valve DTC 45 to set, antilock braking is disabled and the EBCM turns "ON" the ABS warning lamp for the remainder of the ignition cycle. If the malfunction is intermittent, the EBCM will enable the system at the next ignition cycle and a history DTC 45 will be present.

IMPORTANT
^ The auto test is performed once during each ignition cycle when the vehicle reaches approximately 4 mph This test may be heard and felt while it is taking place and should be considered a normal mode of operation. This test can also be performed by using the Tech 1 in "Misc. Tests" mode F4.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks the integrity of CKTs 826 and 856, the LF valve solenoid circuitry internal to the BPM valve and the LF valve solenoid coil.
2. This test checks for a short to ground in CKT 826
3. This test checks for a short to B+ in CKT 826.
4. This test checks for connector or wiring malfunctions which may cause an intermittent condition.
5. This test uses the Tech 1 to check for proper valve solenoid operation.
6. This test determines whether the DTC was set by an intermittent condition or an EBCM malfunction.
7. This test determines whether the malfunction revealed in Step 1 is due to a malfunctioning BPM valve or a wiring malfunction.
8. This test determines whether the malfunction is an open CKT 826 or a short from CKT 826 to CKT 856.

DIAGNOSTIC AIDS
All tests which require a connection to Pinout Box Pin 20 are using this pin as ground. This assumes that the integrity of ground CKT 51 has been maintained.
It is important that a thorough inspection of the wiring and connectors be performed prior to road testing the vehicle. This DTC can only be set when the vehicle is in motion. Failure to properly inspect wiring and connectors may result in a misdiagnosis of a faulty BPM valve or EBCM.
If DTCs 41 and 45 are both set the malfunction is likely to be a short to B+ on CKT 827.
If DTCs 45 and 55 are both set the malfunction is likely to be a short to B+ on CKT 826.