Hello. I have a 97 Deville. Several times each day, the "Traction Engaged" message is displayed on my dash and I hear a grinding sound. This happens daily, dispite the fact that road conditions are dry. I am able to press the button in the glove box to turn the traction off. But this is only a temporary fix. In a previous thread (Transmission Problem) it has been suggested that this problem may be caused by a faulty sensor. Any additional information regarding an approach to further analyze or repair is appreciated.

Steve:)

It could be a wheel speed sensor. You need to check the computers codes to confirm this. Press and hold the on/off and warmer button on the climate controls to get the codes to display.

It says that I have PCM 1520 and PCM 1527 codes. Then it asks PCM?

No codes for the following: IPC, ACM, SDM, TCS, PZM, IRC, RFA, MSM, or MMM.

It says that I have PCM 1520 and PCM 1527 codes. Then it asks PCM?

No codes for the following: IPC, ACM, SDM, TCS, PZM, IRC, RFA, MSM, or MMM.


DTC P1520 Transmission Range Switch Circuit

DTC P1527 Transmission Range to Pressure Switch Correlation

DTC P1520 Transmission Range Switch Circuit




Circuit Description
This vehicle uses an electronic gear indicator display. There are four inputs which are switches to ground that each have a unique switch pattern. All four of these inputs are housed and operate together in the Transaxle Range Switch. The PCM uses the combination of the switch patterns to determine the gear selected by the driver. This information is then sent by serial data to the IPC for gear indicator display. This diagnostic test monitors the transaxle range switch for false outputs. The DTC will set if the transaxle range switch is indicating a switch pattern that the PCM does not recognize.

Conditions for Setting the DTC
Test Conditions
Test continuously.
DTCs P0502 or P0503 not set.
Failure Condition
Transaxle range switch indicating an illegal combination for 3.3 seconds

Action Taken When the DTC Sets
PCM will substitute park/neutral status from transaxle pressure switch for transaxle range switch park/neutral status.
The Malfunction Indicator Lamp (MIL) will not illuminate.
The PCM will command a message to be displayed.
The PCM may record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records.
Conditions for Clearing the Message/DTC

The PCM will turn the message OFF after one run and pass of the diagnostic test.
A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
Use a scan tool to clear DTCs.
Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.
Diagnostic Aids

Important
Check shifter for normal freedom of movement.

The gear select display will box all gear indications and flash on and off if an invalid or suspect gear position is received by the PCM. This will normally occur if the gear selector is not fully in a gear position. When a valid gear position is attained, the gear select display will immediately display the correct position. If the PRNDL on the IPC is flashing, this may be an indication that the shift cable and/or Transaxle Range Switch is out of adjustment.


The modes (circuits) are displayed in order A/B/C/P.
OFF indicates the circuit low (switched / shorted to ground).
ON indicates the circuit is high (open).
If the DTC sets and the PRNDL on the IPC is flashing while driving or when the driver in not moving the gear selector lever, record the transaxle range switch input and compare the values to the chart. For example, if the driver was driving in overdrive when the PRNDL on the IPC flashed and the input read ON, OFF, ON, ON, check for an intermittent open in circuit 773.
Manipulate related wiring and connectors while observing the transaxle range switch input. If an intermittent is induced, the digit corresponding to the circuit will change. If wiring and connectors check out OK, substitute a known good transaxle range switch and recheck.
Depending on the Scan Tool used, the transmission fluid pressure switch parameter and the gear select lever parameter may have two different titles.For example: when using a Tech 1 on a 1996 vehicle the gear select lever parameter would be named Sel. Lever Sw. and Sel. Lever Sw. A/B/C/P. The same vehicle and parameter using a Tech 2 would be named Transmission Range and T R Switch A/B/C/P. These same parameters may also call the state of the circuit differently. For example: the Tech 1 may indicate ON for an open circuit while the Tech 2 would indicate High for an open circuit. Proper verification of the parameter being observed can be indicated by the inability of the transmission fluid pressure switch to indicate any gear other than Drive 2 when the vehicle is not running (no pressure available).

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.

The adjustment procedures must be done before diagnosis of the system. This step does a comparison of both the transaxle range switch and the transaxle pressure switches. If both displays match in all gear selections then the fault is not present or may have been repaired when the adjustment procedures were performed.

If Trans Range (or TFP Switch) display doesn't match the gear selected then the transaxle pressure switches are at fault.

Checking if the ground circuit to the switch may be at fault.

If a circuit stays ON (High) or OFF (Low) all the time, that circuit or switch is open or shorted to ground.

Step
Action
Value(s)
Yes
No

1
Was the Powertrain On-Board Diagnostic (OBD) System Check performed?
--
Go to Step 2
Go to A Powertrain On Board Diagnostic (OBD) System Check

2

Important
Perform the Park/Neutral Position Switch adjustment procedure and the Shift Cable/Lever adjustment procedure in Section 7 before proceeding with this chart.


Block the vehicle drive wheels to keep the vehicle from rolling forward or backward.
Connect the scan tool.
With the engine running, move the shift lever through each range and observe Trans. Range (or TFP Switch) and Sel. Lever Sw. (or Transmission Range) with a scan tool.
Do the scan tool displays match each other for the range that is selected?
--
Fault not present. Refer to Diagnostic Aids
Go to Step 3

3
Does Trans Range (TFP Switch) match each range selected?
--
Go to Step 4
Go to DTC P1810 in Section 7

4
With a scan tool observe the Sel. Lever Sw A/B/C/P (or Trans Range A/B/C/P) display.

Do all the modes display ON (or High).
--
Go to Step 13
Go to Step 5

5
Do any of the modes (A / B / C / P) stay ON (High) or OFF (Low) all of the time regardless of selector position?
--
Go to Step 6
Go to Step 15

6
Do the mode(s) that did not change always display ON (High)?
--
Go to Step 9
Go to Step 7

7
Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C1.
Disconnect the Transaxle Range Switch.
Using DMM J 39200 measure the resistance to ground on the circuit(s) that were always OFF (Low).
Mode A is CKT 771.
Mode B is CKT 772.
Mode C is CKT 773.
Mode P is CKT 776.
Is the resistance on the tested CKT(s) less than the value specified?
5 ohms
Go to Step 8
Go to Step 11

8
Repair the short to ground in the CKT(s) that have low or no resistance to ground.

Is the repair complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

9
Record the fluid life indexes, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C1.
Disconnect the Transaxle Range Switch.
Using DMM J 39200 measure the resistance between the Transaxle Range Switch connector and the PCM connector C1 terminals on the circuit(s) that were always ON (High).
Mode A is CKT 771.
Mode B is CKT 772.
Mode C is CKT 773.
Mode P is CKT 776.
Is the resistance on the tested CKT(s) more than the value specified?
5 ohms
Go to Step 10
Go to Step 12

10
Repair the open in the CKT(s) that have high or infinite resistance.

Is the repair complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

11
Reconnect PCM connector C1, leave the range switch disconnected.
Check the Sel. Lever Sw A/B/C/P (or Trans Range A/B/C/P) display with the key ON.
Do all modes indicate ON?
--
Go to Step 16
Go to Step 17

12
Reconnect PCM connector C1, leave the range switch disconnected.
Check the Sel. Lever Sw A/B/C/P (or Trans Range A/B/C/P) display with the key ON.
At the transaxle range switch connector (harness side), jumper to ground the CKT(s) that were always ON (High).
Does the display change from ON (High) to OFF (Low) when the circuit is jumpered to ground?
--
Go to Step 15
Go to Step 17

13
Turn the key to LOCK.
Disconnect the transaxle range switch ground connector.
Using DMM J 39200 measure the resistance to ground on CKT 451.
Is the resistance the same or less than the value specified?
5 ohms
Go to Step 15
Go to Step 14

14
Repair the open/high resistance in the Transaxle Range Switch ground circuit (CKT 451).

Is the repair complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

15
Check for two or more mode circuits shorted together, if okay check the terminal contact at the transaxle range switch.
Repair if necessary.
Was a repair made?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
Go to Step 16

16
Replace the transaxle range switch.

Is the replacement complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

17
Check the terminal contact at the PCM.
Repair if necessary.
Was a repair made?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
Go to Step 18

18
Replace the PCM. Refer to PCM Replacement/Programming .

Is the replacement complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--



--------------------------------------------------------------------------------
Document ID# 45239
1997 Cadillac DeVille

DTC P1527 Transmission Range to Pressure Switch Correlation
Refer to Electrical Schematic Diagrams for wiring view.

Circuit Description
This vehicle uses an electronic gear indicator display. There are four inputs which are switches to ground that each have a unique switch pattern. All four of these inputs are housed and operate together in the Transaxle Range Switch. The PCM uses the combination of the switch patterns to determine the gear selected by the driver. This information is then sent by serial data to the IPC for gear indicator display. When the Test Conditions are true this test compares the gear indicated by the Transaxle Range Switch to the gear selected from the Transmission Fluid Pressure Manual Valve Position Switch (pressure switch). If the gear indicated is not the same for both, this DTC is set.

Conditions for Setting the DTC
Test Conditions
Engine running continously for 5 seconds.
Ignition voltage is between 10 and 16 volts.
Transaxle Range (select lever) switch does not indicate an illegal position.
Transmission Fluid Pressure Manual Valve Position Switch (pressure switch) does not indicate an illegal position.
DTC P1810 has ran and passed.
Failure Condition
The Transaxle Range switch and the Transmission Fluid Pressure Manual Valve Position Switch (pressure switch) indicate different gears for at least 7.8 seconds.

Action Taken When the DTC Sets

The Malfunction Indicator Lamp (MIL) will not illuminate.
No message will be displayed.
Conditions for Clearing the MIL/DTC

A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test.
A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
Use a scan tool to clear DTCs.
Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation.
Diagnostic Aids
The modes (circuits) are displayed in order A/B/C/P.
OFF indicates the circuit low (switched / shorted to ground).
ON indicates the circuit is high (open).
If the DTC sets and the PRNDL on the IPC is flashing while driving or when the driver in not moving the gear selector lever, record the transaxle range switch input and compare the values to the chart. For example, if the driver was driving in overdrive when the PRNDL on the IPC flashed and the input read ON, OFF, ON, ON, check for an intermittent open in circuit 773.
Manipulate related wiring and connectors while observing the transaxle range switch input. If an intermittent is induced, the digit corresponding to the circuit will change.
Use the Failure Records to help determine which switch was reading incorrectly. If the DTC set and the pressure switch indicated D1and the select lever switch indicated P/N and the engine sensors (MAP, TP, MAF etc.) appear to indicate the vehicle was in Park or Neutral then check the pressure switch/circuits for an intermittent fault.

Depending on the Scan Tool used, the transmission fluid pressure switch parameter and the gear select lever parameter may have two different titles.For example: when using a Tech 1 on a 1996 vehicle the gear select lever parameter would be named Sel. Lever Sw. and Sel. Lever Sw. A/B/C/P. The same vehicle and parameter using a Tech 2 would be named Transmission Range and T R Switch A/B/C/P. These same parameters may also call the state of the circuit differently. For example: the Tech 1 may indicate ON for an open circuit while the Tech 2 would indicate High for an open circuit. Proper verification of the parameter being observed can be indicated by the inability of the transmission fluid pressure switch to indicate any gear other than Drive 2 when the vehicle is not running (no pressure available).

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.

The adjustment procedures must be done before diagnosis of the system. This step does a comparison of both the transaxle range switch and the transaxle pressure switches. If both displays match in all gear selections then the fault is not present or may have been repaired when the adjustment procedures were performed.

If TFP Switch doesn't match the gear selected then the transaxle pressure switches are at fault.

Checking if the ground circuit to the switch may be at fault.

If a circuit stays ON (High) or OFF (Low) all the time, that circuit or switch is open or shorted to ground.

A few conditions could occur in the Transmission Fluid Pressure Manual Valve Position Switch and circuits which may not set a DTC P1810. Only one of these faults could be a circuit only or PCM fault.

Step
Action
Value(s)
Yes
No

1
Was the Powertrain On-Board Diagnostic (OBD) System Check performed?
--
Go to Step 2
Go to A Powertrain On Board Diagnostic (OBD) System Check

2

Important
Perform the Park/Neutral Position Switch adjustment procedure and the Shift Cable/Lever adjustment procedure in Section 7 before proceeding with this chart.


Block the vehicle drive wheels to keep the vehicle from rolling forward or backward.
Connect the scan tool.
With the engine running, move the shift lever through each range and observe TFP Switch (pressure) and Transmission Range.
Do the scan tool displays match each other for the range that is selected?
--
Fault not present. Refer to Diagnostic Aids
Go to Step 3

3
Does TFP Switch (pressure) match each range selected?
--
Go to Step 4
Go to Step 17

4
Turn the key ON.
Using the scan tool observe the Trans Range A/B/C/P display.
Do all the modes display ON (High).
--
Go to Step 13
Go to Step 5

5
Do any of the modes (A / B / C / P) stay ON (High) or OFF (Low) all of the time regardless of selector position?
--
Go to Step 6
Go to Step 15

6
Do the mode(s) that did not change always display ON (High)?
--
Go to Step 9
Go to Step 7

7
Store fluid life, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C1.
Disconnect the Transaxle Range Switch.
Using DVM J 39200 measure the resistance to ground on the circuit(s) that were always OFF (Low).
Mode A is CKT 771.
Mode B is CKT 772.
Mode C is CKT 773.
Mode P is CKT 776.
Is the resistance on the tested CKT(s) less than the value specified?
5 ohms
Go to Step 8
Go to Step 11

8
Repair the short to ground in the CKT(s) that have low or no resistance to ground.

Is the repair complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

9
Store fluid life, turn the key to LOCK and wait 30 seconds.
Disconnect PCM connector C1.
Disconnect the Transaxle Range Switch.
Using DVM J 39200 measure the resistance between the Transaxle Range Switch connector and the PCM connector C1 terminals on the circuit(s) that were always ON (High).
Mode A is CKT 771.
Mode B is CKT 772.
Mode C is CKT 773.
Mode P is CKT 776.
Is the resistance on the tested CKT(s) more than the value specified?
5 ohms
Go to Step 10
Go to Step 12

10
Repair the open in the CKT(s) that have high or infinite resistance.

Is the repair complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

11
Reconnect PCM connector C1, leave the range switch disconnected.
Check the Trans Range A/B/C/P display with the key ON.
Do all modes indicate ON (High)?
--
Go to Step 16
Go to Step 23

12
Reconnect PCM connector C1, leave the range switch disconnected.
Check the Trans Range A/B/C/P display with the key ON.
At the transaxle range switch connector (harness side), jumper to ground the CKT(s) that were always ON (High).
Does the display change from ON (High) to OFF (Low) when the circuit is jumpered to ground?
--
Go to Step 15
Go to Step 23

13
Turn the key to LOCK.
Disconnect the transaxle range switch ground connector.
Using DVM J 39200 measure the resistance to ground on CKT 451.
Is the resistance the same or less than the value specified?
5 ohms
Go to Step 15
Go to Step 14

14
Repair the open/high resistance in CKT 451.

Is the repair complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

15
Check for two or more mode circuits shorted together, if okay check the terminal contact at the transaxle range switch.
Repair if necessary.
Was a repair made?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
Go to Step 16

16
Replace the transaxle range switch.

Is the replacement complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

17
Is DTC P1810 also set?
--
Go to DTC P1810 diagnosis
Go to Step 18

18
With the engine running, does the Trans Range (pressure) match in P, R, N, and D4 but not in D3, D2 and D1?
--
Go to Step 20
Go to Step 19

19
Replace the Transmission Fluid Pressure Manual Valve Position Switch assembly.

Is the replacement complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

20
Disconnect the Transaxle 20 way connector and shift through gear range.

Does the display ALWAYS indicate P/N?
--
Go to Step 21
Go to Step 22

21
Check for a shorted to ground Transaxle Range B input circuit between the Transaxle 20-way connector and the PCM.

Was a shorted condition repaired?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
Go to Step 23

22
A short to ground condition exists between the Transaxle 20-way connector and the transmission Fluid Pressure Manual Valve Position Switch or the Fluid Pressure Manual Valve Position Switch is faulty.
Repair or replace as necessary
Is the repair complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

23
Check the terminal contact at the PCM.
Repair if necessary.
Was a repair made?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
Go to Step 24

24
Replace the PCM. Refer to PCM Replacement/Programming .

Is the replacement complete?
--
Go to Powertrain Control Module Diagnosis for Verify Repair
--

Wow, above and beyond the call Bbob! I am impressed (not that it matters). I just want to tell you 'Thanks' for all the time and effort you contribute to this forum. I have learned a lot from your posts in the short time I have been here.

Kev

Wow, above and beyond the call Bbob! I am impressed (not that it matters). I just want to tell you 'Thanks' for all the time and effort you contribute to this forum. I have learned a lot from your posts in the short time I have been here.

Kev

You are welcome....and easy....LOL LOL Don't be too impressed. All that was just a cut and paste from some service info that every dealer has access to....

You are welcome....and easy....LOL LOL Don't be too impressed. All that was just a cut and paste from some service info that every dealer has access to....
I'm impressed that you are generous with sharing the information that is available to you (not all of us can get that so easily) and willing to take the time for it. I also appreciate the patience that you exhibit when dealing with those of us who are ignorant.
Thanks

Kev

YES! Thank you very much. With this information I am now able to make an informed decision regarding potential repairs.

Steve

That was great

The Bbob is my Shepherd. :coolgleam

The Bbob is my Shepherd. :coolgleam
Now that's what I would call pushin it! :cool: Heh heh.

Kev

Hey Kev,

I won't be subject to any nasal discolorment or
be pushing in any stools ;but, Bbob saved me
five (5) grand last month, and is worthy of both
homage and veneration.

In any event, I'm cool and don't get you wrong.
I am keenly aware that we both
truly share mutual respect for the
admirable and credible wisdom that the
Bbob selflessly dispenses to the esteemed
Caddycommunity on an almost daily basis.

Caddy Dudes! Have a good weekend.

TomDeville
:coolgleam