1998 C70 Coupe, AW 50-42 DTC Topic is solved

Post by **RickHaleParker** » 06 Aug 2015, 09:08

Anybody know better then VOL-FCR?
From the AW 50-42 module: Unknown DTC 1C
Transmission has no symptoms.

Post by **precopster** » 06 Aug 2015, 15:33

On my 98 V70R Vol FCR was the only scanner within financial reach that would cancel a transmisssion code that wouldn't exterminate with other scanners.

Post by **RickHaleParker** » 30 Sep 2018, 06:33

Three years and still no clue ... the code will clear but it comes right back.
Reading this code in both VOL-FCR and 850 OBD-II.

Post by **RickHaleParker** » 08 Oct 2018, 05:55

Thanks to esl_97_850_T5 who did an analysis of my diagnostic logs and narrowed this down to two possibilities.

esl_97_850_T5 wrote:
"That leaves these two DTCs as possibilities assuming there is

no flashing in the dash:
* AT-114 -- Mode selector switch, signal too high.
- When: Can be caused by E and S buttons in mid-position
for > 25 sec.
- Symptom: Transmission only operates in Economy mode.
* AT-143 -- Kickdown switch, signal too low.
- When: TCM sees short circuit to ground in
kick-down switch circuit when throttle opening < 85%.
* Be aware: AT-143 can occur when kick-down switch closed,
and TPS signal is too low at wide open throttle"

1. The Kickdown Switch has broken in two at the firewall and is shorted at all times.
2. Kickdown function is hit and miss.
3. Disconnecting the wiring harness from the Kickdown Switch clears the 1C code and it does not come back.

New Throttle Cable with Kickdown Switch ordered from FCP Euro.

I don't drive this '98 C70 Special Edition much. She decided it her car but, she nice enough to let me work on it, pay for it and cover the overhead expenses.

-------------------------------------------------------------------------------------------------------------------
ECU 6E DTC: 1C = AT-143.

AT-143. Kickdown switch

DTC information

A4300526 Condition
The transmission control module (TCM) uses the kick-down switch signal to control functions such as downshifting during rapid acceleration. The kick-down switch closes when the outer sleeve of the accelerator cable is pressed against the switch (when the accelerator pedal (AP) is fully depressed). Diagnostic trouble code (DTC) AT-143 is posted if the transmission control module (TCM) registers a short-circuit to ground in the kick-down switch circuit when the throttle opening is less than 85%.
Caution! Diagnostic trouble code (DTC) AT-143 is posted when the kick-down switch is closed if the throttle position (TP) sensor signal is too low at wide open throttle (WOT) (less than 85%).

Substitute value
No substitution value

Possible source

Short-circuit to ground in signal cable
Defective kick-down switch
Faulty throttle position (TP) sensor signal
Transmission control module (TCM) replaced but throttle position (TP) sensor signal not adapted.

Fault symptoms
No kick-down function.

Post by **abscate** » 08 Oct 2018, 06:47

I don't drive this '98 C70 Special Edition much. She decided it her car but, she nice enough to let me work on it, pay for it and cover the overhead expenses.

They are very smart.

Post by **esl_97_850_T5** » 08 Oct 2018, 12:32

Since apparently the old throttle cable is still in the car, can you use "850 OBD-II" Live OBDII to see what Throttle Position degrees are when ignition at pos II, accelerator pedal fully depressed? Curious if it is < 85% (which is one reason for AT-143) or > 85%? [Of course, any regular OBDII scanner can read that.]

Also, with old cable with the broken Kickdown Switch what does "850 OBD-II" Live AW50-42 report as T/P Voltage when ignition at pos II, accelerator pedal full depressed?

Post by **RickHaleParker** » 09 Oct 2018, 08:33

esl_97_850_T5 wrote: ↑08 Oct 2018, 12:32 Since apparently the old throttle cable is still in the car, can you use "850 OBD-II" Live OBDII to see what Throttle Position degrees are when ignition at pos II, accelerator pedal fully depressed? Curious if it is < 85% (which is one reason for AT-143) or > 85%? [Of course, any regular OBDII scanner can read that.]

Also, with old cable with the broken Kickdown Switch what does "850 OBD-II" Live AW50-42 report as T/P Voltage when ignition at pos II, accelerator pedal full depressed?

Any OBD scanner can read the TP but not the DTC 1C. Torque Pro did not pick up the 1C. We do want to get the full condition profile for this DTC 1C.

I can see why to want to make darn sure this is AT-143. Your current list of known hexadecimal codes has AT-143 listed as "ECU 6E DTC #14: 3F -> AT-143 -- Kickdown switch circuit.". Is the 3F a confirmed, somebody's deductive reasoning or something you got from another list?

Also once I change the Throttle Cable and Kickdown Switch, we lose the conditions that produced the DCT 1C. If we don't take advantage of it now we lose an opportunity.

This is the logic as I got it worked out:

Where 1=Closed and 0=Open.

(TP<85%) + (KD=1) = AT-143
(TP<85%) + (KD=0) ≠ AT-143

(TP>85%) + (KD=1) ≠ AT-143
(TP>85%) + (KD=0) ≠ AT-143

Weather not cooperating, T-storms all week long. 850 OBD-II on my phone is not cooperating, keeps dropping BT connection. Torque Pro still works on the phone so I don't think it is the hardware. I'll load Remix OS and 850 OBD-II on a Flash Drive and see if I can get a working system ..... Might try clearing the phone data on 850 OBD-II.

The test plan.
KD will be monitored with a Ohm meter across the KD wiring harness.
TP and ECU 6E with be monitored with 850 OBD-II.

Set TP to >85% Confirm that KD=1, clear code 1C, see if it sets again.
Set TP to <85% Confirm that KD=1, clear code 1C, see if it sets again.

Disconnect the wiring harness:
Set TP to >85% Confirm that KD=0, clear code 1C, see if it sets again.
Set TP to <85% Confirm that KD=0, clear code 1C, see if it sets again.

Post by **RickHaleParker** » 09 Oct 2018, 08:58

Anybody with a P80 equipped with Motronic 4.3 or 4.4 and a automatic transmission, and has (Volvo850diag, 850 OBD-II or VOL-FCR) can help.

You disconnect the wiring harness to the Kickdown switch and place a jumper wire across the wiring harness, scan for DTCs and report what DTC you get for the transmission and your car's configuration.

To reverse: reconnect the wiring harness and clear the codes.

Post by **RickHaleParker** » 09 Oct 2018, 13:39

Got a break in the weather and 850 OBD-II up and going on Remix OS. Got the same problems with 850 OBD-II and Remix OS as I do on the phone. I have seen this before and had to wait until the next update for 850 OBD-II to work again.

I think 850 OBD-II does not like my ELM357 BT interfaces, which are the BAFX Products OBDII Diagnostic interface and the Excel OBDII Scanner. Looks like it time to hunt down a Genuine ELM327 interface. And while I'm at it, find a better OBDII USB cable for VOL-FCR.

Using VOL-FCR: If I hold the accelerator pedal to the floor, the DCT 1C will clear and it does not come back until I release the accelerator pedal ... the correct behavior for AT-143.

Post by **RickHaleParker** » 11 Oct 2018, 20:57

The new Throttle Cable with Kickdown Switch came today. Replaced the old one, DTC 1C (AT-143) is history.

VIDA says to release the Kickdown retaining clips from the cabin side of the firewall, took a look under the dash and decide no way I'm taking all that off. Decided to approach the task from the engine bay side.

My switch was already broken. If your trying to replace a cable and your old one is not broken, I suggest you take a lever and break it.

Pry the mount out of the firewall and fish out anything on the other side of the firewall.

If necessary, dike the ball off the cabin end of the cable.

Pull the old cable out feed the new one in. Install the retainer to the cabin end.

Install the Throttle body end and adjust the slack.

Reconnect the loom.

She says her C70 is much happier now.