Yeah the 1-5-3 code is for the rear O2 sensor on the Turbo models. Do you have a OBDII port under the coin holder in the console? Where you could plug in a DTC reader and get the OBDII codes? I like the Actron 9135 for this. Do you have a rear O2 sensor? If so probably just replace it. But the troubleshooting for the 1-5-3 code is:

Code 1-5-3 (Rear HO2S Signal)

1) If Codes 5-2-2 or 2-1-2 are stored, perform diagnosis for
these codes first. If fault is permanent or intermittent and signal is
too high, perform diagnosis as per Code2-1-2. If fault is permanent
and signal is too low, go to next step. If fault is permanent and
signal is faulty, go to step 8). If fault is intermittent and signal
is too low, go to step 9). If fault is intermittent and signal is
faulty, go to step 10).

2) Turn ignition off. Wait 2 minutes. Disconnect rear HO2S
Gray connector. Connect an ohmmeter between HO2S connector terminal
No. 4 and ground. If ohmmeter shows about 100 k/ohms, go to step 4).
If ohmmeter shows infinite resistance, go to next step. If ohmmeter
shows about zero ohms, check wiring between rear HO2S connector
terminal No. 4 and ECM terminal A34 for a short circuit to ground.

3) Turn ignition off. Disconnect HO2S connector. Ensure ECM
connector terminal contacts are clean and tight. Reconnect ECM.
Connect an ohmmeter between HO2S connector terminal No. 4 and ground.
If ohmmeter reads about 100 k/ohms, source of code is poor contact at
ECM connector. If ohmmeter does not read about 100 k/ohms, check
wiring between rear HO2S connector terminal No. 4 and ECM terminal A34
for an open circuit.

4) Turn ignition off. Disconnect rear HO2S connector. Connect
an ohmmeter between HO2S connector terminal No. 3 and ground. If
ohmmeter reads about 200 ohms, go to step 7). If ohmmeter shows
infinite resistance, go to next step. If ohmmeter shows about zero
ohms, go to step 6).

5) Turn ignition off. Disconnect rear HO2S connector. Ensure
ECM connector terminals are clean and tight. Reconnect ECM. Connect an
ohmmeter between HO2S connector terminal No. 3 and ground. If ohmmeter
reads about 200 ohms, source of code is poor contact in ECM connector.
If ohmmeter does not read about 200 ohms, check wiring between rear
HO2S connector terminal No. 3 and ECM terminal A19 for an open
circuit.

6) Turn ignition off. Disconnect rear HO2S connector.
Disconnect front HO2S Black connector. Connect an ohmmeter between
rear HO2S connector terminal No. 3 and ground. If ohmmeter reads about
200 ohms, test system using a new front HO2S. If ohmmeter does not
read about 200 ohms, check wiring between front HO2S connector
terminal No. 3 and ECM terminal A33, and wiring between rear HO2S
connector terminal No. 3 and ECM terminal A19 for a short to ground.

7) Turn ignition off. Ensure rear HO2S is connected. Start
and run engine at idle. Check voltage at rear HO2S. Voltage signal
should have left its bottom setting (-.165 volt) and stabilized
between .1-.9 volt within about 10 minutes. If reading is okay, source
of code is poor contact at rear HO2S connector. If reading is not
okay, retest using new rear HO2S.

8) If fault is permanent and signal is faulty, turn ignition
off. Wait about 2 minutes. Disconnect rear HO2S Gray connector.
Connect an ohmmeter between HO2S connector terminals No. 3 and 4. If
ohmmeter reads infinite resistance, check wiring between rear HO2S
connector terminal No. 4 and ECM connector terminal A34 for a short
circuit to rear HO2S connector terminal No. 3 and ECM connector
terminal A19. If ohmmeter does not read infinite resistance, test
using new HO2S.

9) If fault is intermittent and signal is too low, check
wiring between rear HO2S connector terminal No. 4 and ECM terminal
A34, and between rear HO2S connector terminal No. 3 and ECM terminal
A19 for an open circuit. Check ECM and rear HO2S connector for loose
connection. Check wiring between rear HO2S connector terminal No. 4
and ECM terminal A34 for an intermittent short circuit to ground. Also
check wiring between front HO2S connector terminal No. 3 and ECM
terminal A33, and wiring between rear HO2S connector terminal No. 3
and ECM terminal A19 for an intermittent short circuit to ground.

10) If fault is intermittent and signal is faulty, check
wiring between rear HO2S connector terminal No. 4 and ECM connector
terminal A34 for an intermittent short circuit of wire between rear
HO2S connector terminal No. 3 and ECM connector A19.


Good luck......... Mike