Symptom:
P0688-ASD RELAY SENSE CIRCUIT LOW
When Monitored and Set Condition:
P0688-ASD RELAY SENSE CIRCUIT LOW
When Monitored: With ignition key on. Battery voltage greater than 10 volts.
Set Condition: No voltage sensed at the PCM when the ASD relay is energized.
POSSIBLE CAUSES
VERIFY ASD DTC
ASD RELAY
(A16) FUSED B+ CIRCUITS
(A142) ASD RELAY OUTPUT CIRCUIT OPEN (NO START)
(A142) ASD RELAY OUTPUT CIRCUIT SHORTED TO GROUND
(A142) ASD RELAY OUTPUT CIRCUIT OPEN (START)
PCM
TEST ACTION APPLICABILITY
1 NOTE: Diagnose P0685 - Auto Shutdown Relay Control Circuit first if set
along with this DTC.
With the DRBIIIt, erase the DTC.
Attempt to start the engine. If the engine will not start, crank the engine for at least
15 seconds. It may be necessary to repeat several times.
Does the DTC reset?
Yes ! Go To 2
No ! Refer to the INTERMITTENT CONDITION Symptom (Diagnostic
Procedure).
2 Attempt to start the engine.
Does the engine start?
Yes ! Go To 3
No ! Go To 4
.
3 Turn the ignition off.
Remove the ASD Relay from the PDC.
Disconnect the PCM harness connectors.
Measure the resistance of the (A142) ASD Relay Output circuit from the PDC to the
appropriate terminals of the PCM connector
Is the resistance below 5.0 ohms?
Yes ! Go To 8
No ! Repair the open in the (A142) ASD Relay Output circuit.
4 Turn the ignition off.
Install a substitute relay in place of the ASD Relay.
Ignition on, engine not running.
With the DRBIIIt, erase DTCs.
Attempt to start the engine.
With the DRBIIIt, read DTCs.
Does the DTC reset?
Yes ! Go To 5
No ! Replace the ASD Relay.
5 Turn the ignition off.
Remove the ASD Relay from the PDC.
Using a 12-volt test light connect to ground, probe the (A16) Fused B+ circuits in the
PDC.
Does the test light illuminate brightly?
Yes ! Go To 6
No ! Repair the open or short to ground in the (A16) Fused B+ circuits.
Inspect the related fuse and repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 5.
6 Disconnect the PCM harness connectors.
Measure the resistance of the (A142) ASD Relay Output circuit from the PDC to the
appropriate terminals of the PCM connector.
Is the resistance below 5.0 ohms?
Yes ! Go To 7
No ! Repair the open in the (A142) ASD Relay Output circuit.
.
TEST ACTION APPLICABILITY
7 Measure the resistance between ground and the (A142) ASD Relay Output circuit at
the Relay connection.
Is the resistance below 100 ohms?
Yes ! Repair the short to ground in the (A142) ASD Relay Output
circuit.
No ! Go To 8
8 NOTE: Before continuing, check the PCM harness connector terminals for
corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay
particular attention to all Power and Ground circuits.
If there are no possible causes remaining, view repair.
Repair:
Replace and program the Powertrain Control Module per Service
Information.
.
POWERTRAIN CONTROL MODULE C3 - WHITE 38 WAY
CAV / CIRCUIT / FUNCTION1 / - / -
2 / - / -
3 / K51 20DB/YL / ASD RELAY CONTROL
4 / - / -
5 / V35 20LG/RD / S/C VENT CONTROL
6 / C24 20DB/PK / RADIATOR FAN RELAY CONTROL
7 / V32 18VT/YL / SPEED CONTROL SUPPLY
8 / K106 20WT/DG / NVLD SOLENOID CONTROL
9 / K199 18BR/WT / O2 1/2 HEATER CONTROL
10 / K399 18BR/GY / O2 2/2 HEATER CONTROL
11 / C13 20LB/OR / A/C CLUTCH RELAY CONTROL
12 / V36 20VT/DG / S/C VACUUM CONTROL
13 / - / -
14 / - / -
15 / - / -
16 / - / -
17 / - / -
18 / - / -
19 / A142 16DG/OR / ASD RELAY OUTPUT
20 / K52 18PK/BK / EVAP/PURGE CONTROL
21 / T41 18DG/GY A/T / TRS T41 SENSE
21 / T41 18BK/WT M/T / TRS T41 SENSE
22 / - / -
23 / V40 20WT/PK / BRAKE SWITCH SIGNAL
24 / - / -
25 / - / -
26 / - / -
27 / - / -
28 / A142 16DG/OR / ASD RELAY OUTPUT
29 / K70 18DB/BR / EVAP PURGE SIGNAL
30 / - / -
31 / - / -
32 / K118 20PK/YL / AAT SIGNAL
33 / K226 18DB/WT / FUEL LEVEL SIGNAL
34 / V37 18VT/TN / S/C SWITCH SIGNAL
35 / K107 20OR / NVLD SWITCH SENSE
36 / - / -
37 / K31 20BR / FUEL PUMP RELAY CONTROL
38 / T752 18DG/OR / STARTER RELAY CONTROL