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

[esl_97_850_T5]

Rick, thanks a bundle for doing all the research!!

1. I confirmed (via the "disconnect Kickdown Switch electrical connector, then jumpering female connector leads, then turn ignition on, then read ECU 6E (AW50-42) DTCs" test) that my '98 S70 GLT also produces ECU 6E DTC 1C.

I also duplicated the behaviors you saw of:

- DTC 1C could be erased when pedal fully depressed and OBDII Throttle Position (reported to M44 by TP Sensor attached to Throttle body) at ~87% > 85% trigger, and

- DTC 1C then returns when pedal let off a little so Throttle Position < 85%, and

- once Kickdown Switch electrical connector is reattached to fulfill its destiny, the DTC 1C does not manifest regardless what the Throttle Position is, ie, things returned to normal (like after you replaced your Throttle cable and Kickdown Switch combo).

2. KWPD3B0 interpreter will be updated accordingly in the next few days to show the association:

ECU 6E DTC 1C -> AT-143 -- Kickdown problem (...exact verbage yet to be decided...)

3. I wished my now-junked '97 850 T5 was still around so the "disconnect Kickdown Switch electrical connector, jumper female connector leads, turn ignition to pos II, read ECU 6E (AW50-42) DTCs" test could be performed on the 850 to see if 850 ECU 6E generates DTC 3F (as Brick-Diag Free v0.0.6.6 suggests for AW50-42 error 1-4-3) or DTC 1C.

Maybe someone else with an 850 can make that test, and perform either a volvo850diag ECU 6E "Read DTCs" (or xiaotec "850 OBD-II" Android app "Scan"), then use KWPD3B0 interpreter to interpret the resultant volvo850diag_yyyymmdd_hhmmss.log (or 850log.txt) log.

Thanks again, Rick.

[RickHaleParker]

ECU 6E DTC 1C -> AT-143 -- Kickdown problem (...exact verbage yet to be decided...)

VIDA pretty much covers possible sources. The only other possible sources I can think of are, improperly adjusted throttle cable or a excessively stretched throttle cable.

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From VIDA:

AT-143. Kickdown switch

DTC information
en-US0800c8af80a1474f en-US0800c8af80a14802

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.

[esl_97_850_T5]

Nice to know VIDA has same info as the OTP Volvo 850 DVD.

I had already decided to include all those in the explanation. Just don't know how I'll word it yet, other than "Kickdown" will very likely be the first word.

[RickHaleParker]

"Kickdown Circuit" ?

How many characters will the description field hold?