EFI throttle loss.

[Big n Lifted]

Can anyone help.
I have a manual 96 Bighorn. When I de excellerate hard or coast down hill in a low gear I get total throttle loss. The check engine light comes on when this happens. To regain throttle I have to turn off ignition quickly then turn back on. This tends to reset everything including engine light. I have taken a flash code reading of 21 and 42. 21 relates to TPS which I have changed but makes no difference. TPS on this model is on the pedal. I have searched for code 42 but everything tells me that it's a unknown code.
Has anyone else had this problem or know of a fix.

[Mattman]

What motor?

[Crash bandicoot]

Isuzu Check Engine Light Trouble Code Info
Isuzu Trouble codes
12 No tach signal to ECM – No Distributor Reference Pulses{4}
13 Oxygen sensor or circuit

14


Coolant Temperature Sensor Circuit

High Coolant Temperature{5}

14A


High Coolant Temperature{6}

14B


Low Coolant Temperature{6}

15


Coolant Temperature Sensor Circuit

Low Coolant Temperature{5}{7}
16 Same as 15

21


TP Sensor And/Or Idle Switch

MAP Sensor{1}

TP Sensor, Voltage High{5}{7}
Throttle valve switch/Wide Open Throttle (WOT) position sensor, 1989 Manifold Absolute Pressure (MAP) circuit failure
Throttle Position Sensor (TPS) – V6 models

21A


TP Sensor, Voltage High{6}

21B


TP Sensor, Voltage Low{6}
22 Starter signal system/1988 and 1989 fuel cut solenoid circuit failure

TP Sensor

TP Sensor, Voltage Low{5}{7}

No Starter Signal{8}

Fuel Cut Off Relay{4}

23


MAT Sensor

MAT Sensor, Low Temp{7}

M/C Solenoid Circuit{4}

Mixture control solenoid circuit failure – 1987 and 1995 Amigo/Pick-up, 1989 to 1994 V6 models

Power transistor circuit – 1988 to 1994 four-cylinder models
Intake Air Temperature sensor voltage high – turbo, 1989 to 1995 1.6L, 1.8L, 3.2L vehicles

23A


MAT Sensor, Low Temp{6}

23B


MAT Sensor, High Temp{6}
24 Vehicle Speed Sensor (VSS) circuit – V6 models
Pressure regulator vacuum switching valve – 1988 to 1994 four-cylinder, also Impulse non-turbo

25


MAT Sensor

Vacuum Switching Valve{4}{9}

MAT Sensor, High Temp{7}
Intake Air Temperature sensor voltage high – turbo, 1989 to 1995 1.6L, 1.8L, 3.2L vehicles
AIR VSV circuit failure

26


Canister Vacuum Switching Valve{4}

VSV System{9}

27


VSV System{9}

Constant Voltage High From VSV To ECM{4}
Fuel injector driver transistor

31


No Ignition Reference Pulses To ECM{4}

Wastegate Control{7}{8}
No ignition reference to ECM – 1988 and 1989 models
32 Exhaust Gas Recirculation (EGR) system failure

33


MAP Sensor

MAP Sensor, Voltage High{5}{7}

Fuel Injector{9}

33A


MAP Sensor, Voltage High–Low{6}

33B


MAP Sensor, Voltage Low–High{6}

34


MAP Sensor{8}{11}

MAP Sensor, Voltage Low{5}

EGR Gas Sensor Circuit{4}{7}

Fuel Injector{10}

35


MAP Sensor Constant Voltage High{4}

Power Transistor System{9}

36


MAP Sensor Circuit{4}

41


Crank Angle Sensor{9}

Cam Signal{7}

42


Fuel Cut Off Relay{4}

Electronic Spark Timing{5}

Ignition Control Circuit{6}{8}
43 Throttle valve switch/Wide Open Throttle (WOT) position sensor {9}
Electronic spark control failure – V6 models
Idle contact switch always closed (1988 to 1994 four-cylinder, also Impulse non-turbo)
1989 Manifold Absolute Pressure (MAP) circuit failure
Knock sensor (1989 to 1995 1.6L, 3.2L) {8}

44


O2S Lean

Fuel Metering{9}

45


Oxygen sensor (rich condition indicated)

Fuel Metering{9}

51


PROM{2}{8}

Fuel Cut Solenoid Circuit And/Or ECM{3} carbureted four-cylinder models

ECM{6}

MEM-CAL{7}

PROM, Cal-Park & ECM{5}

ROM and/or RAM{9}

52


ECM{4}

EEPROM{8}

ROM and/or RAM{9}

PROM, Cal-Park & ECM{5}

53


Switching Valve And/Or ECM{4}

Vacuum Switching Valve{9}

54


M/C (mixture control) Solenoid Circuit And/Or ECM{2}

Vacuum Control Solenoid And/Or ECM{3}

Power Transistor System{9}

Fuel Pump, Voltage Low{5}{8}
Shorted vacuum control solenoid, Faulty Electronic Control Module (ECM) – 1988 and 1989 models

55


ECM{4}{8}

PROM, Cal-Park & ECM{5}
Faulty Electronic Control Module (ECM) or oxygen sensor
61 Air flow sensor circuit failure {9}
62 Air flow sensor circuit failure {9}
63 Vehicle Speed Sensor (VSS) circuit {9}
64 Fuel injector driver transistor {9}

65
Throttle valve switch/Wide Open Throttle (WOT) position sensor, 1989 Manifold Absolute Pressure (MAP) circuit failure

Full throttle switch always on
66 Knock sensor circuit failure {9}
71 Throttle position switch signal abnormal {9}
72 VSV for EGR system short or open {9}
73 Same as 72 transister or ground {9}

[catalystracing]

Wow awesome lot of info, this forum is brilliant for helping each other out.

[Big n Lifted]

Thanks Crash that's a lot of codes. Some info that I have left out, so to keep you all in the loop. The motor is a 3.1td 4jg2. Also my speedo was at that intermittent working stage. Speedo finally gave up the other day completely. I got myself a new speed sensor but hadn't got round to fitting it as was concentrating on throttle problem. I have a feeling that these two may be related. So I will fit sensor and let you know what the out come is.
Thanks again Crash for the codes.

[Crash bandicoot]

Okay ignore 42 for now...that is the result of the fault.

It's basically saying your engine has turned off when it wasn't sposed too and the ecu flashes up said fault no ignition no fuel etc.

IF your speedo is crook or the sender is crook you would have got code 12

so that was working at the time of the fault.

21 doesn't nessassarily mean the tps...it could have been the voltage feed too or from the tps which is crook..once the ecu loses that signal it stalls, by the sounds of the symptoms it could be a crook feed.

Is it a fly by wire throttle by any chance?

[Big n Lifted]

Yes it is fly by wire. I have just been out and fitted speed sensor. Been for a drive and throttle problem has disappeared. Seems my hunch was right. Will go for a longer drive tomorrow to confirm its all good.

[Big n Lifted]

Been for a good drive today and no problems.
Fitted old crook speed sensor back on and first down hill over run I got total throttle loss.
Refitted new speed sensor and all good again.
So to wrap this topic up;
If you have a crook speed sensor in a 96 EFI 4jg2 bighorn you will loose throttle on over run.
Quick fix is to turn ignition off then back on again.
Would strongly recommend that you do not do this while turning a corner as your steering lock may come on.
Or keep RPM under 1500 when going down hill as this seems to stop the loss.
Happy Soozooing folks.....